diff --git a/src/libs/utils/fancymainwindow.cpp b/src/libs/utils/fancymainwindow.cpp
index 1c241b432e6..c3f79374cba 100644
--- a/src/libs/utils/fancymainwindow.cpp
+++ b/src/libs/utils/fancymainwindow.cpp
@@ -25,6 +25,7 @@
 
 static const char ShowCentralWidgetKey[] = "ShowCentralWidget";
 static const char StateKey[] = "State";
+static const char HiddenDockAreasKey[] = "HiddenDockAreas";
 
 static const int settingsVersion = 2;
 static const char dockWidgetActiveState[] = "DockWidgetActiveState";
@@ -37,12 +38,16 @@ struct FancyMainWindowPrivate
 {
     FancyMainWindowPrivate(FancyMainWindow *parent);
 
+    QVariantHash hiddenDockAreasToHash() const;
+    void restoreHiddenDockAreasFromHash(const QVariantHash &hash);
+
     FancyMainWindow *q;
 
     bool m_handleDockVisibilityChanges;
     QAction m_showCentralWidget;
     QAction m_menuSeparator1;
     QAction m_resetLayoutAction;
+    QHash<int, QList<QDockWidget *>> m_hiddenAreas; // Qt::DockWidgetArea -> dock widgets
 };
 
 class DockWidget : public QDockWidget
@@ -217,12 +222,7 @@ public:
                         : QSize(titleMinWidth, titleInactiveHeight);
     }
 
-    QList<QDockWidget *> docksInArea() const
-    {
-        return filtered(q->q->dockWidgets(), [this, area = q->q->dockWidgetArea(q)](QDockWidget *w) {
-            return w->isVisible() && q->q->dockWidgetArea(w) == area;
-        });
-    }
+    QList<QDockWidget *> docksInArea() const { return q->q->docksInArea(q->q->dockWidgetArea(q)); }
 
     bool supportsCollapse() const
     {
@@ -428,11 +428,50 @@ FancyMainWindowPrivate::FancyMainWindowPrivate(FancyMainWindow *parent)
     });
 }
 
+QVariantHash FancyMainWindowPrivate::hiddenDockAreasToHash() const
+{
+    QHash<QString, QVariant> hash;
+    for (auto it = m_hiddenAreas.constKeyValueBegin(); it != m_hiddenAreas.constKeyValueEnd();
+         ++it) {
+        hash.insert(QString::number(it->first),
+                    transform(it->second, [](QDockWidget *w) { return w->objectName(); }));
+    }
+    return hash;
+}
+
+void FancyMainWindowPrivate::restoreHiddenDockAreasFromHash(const QVariantHash &hash)
+{
+    m_hiddenAreas.clear();
+    const QList<QDockWidget *> docks = q->dockWidgets();
+    for (auto it = hash.constKeyValueBegin(); it != hash.constKeyValueEnd(); ++it) {
+        bool ok;
+        const int area = it->first.toInt(&ok);
+        if (!ok
+            || (area != Qt::LeftDockWidgetArea && area != Qt::TopDockWidgetArea
+                && area != Qt::RightDockWidgetArea && area != Qt::BottomDockWidgetArea)) {
+            continue;
+        }
+        QList<QDockWidget *> hiddenDocks;
+        const QStringList names = it->second.toStringList();
+        for (const QString &name : names) {
+            QDockWidget *dock = findOrDefault(docks, [name](QDockWidget *w) {
+                return w->objectName() == name;
+            });
+            if (dock)
+                hiddenDocks.append(dock);
+        }
+        if (!hiddenDocks.isEmpty())
+            m_hiddenAreas.insert(area, hiddenDocks);
+    }
+}
+
 FancyMainWindow::FancyMainWindow(QWidget *parent) :
     QMainWindow(parent), d(new FancyMainWindowPrivate(this))
 {
-    connect(&d->m_resetLayoutAction, &QAction::triggered,
-            this, &FancyMainWindow::resetLayout);
+    connect(&d->m_resetLayoutAction, &QAction::triggered, this, [this] {
+        d->m_hiddenAreas.clear();
+        emit resetLayout();
+    });
 }
 
 FancyMainWindow::~FancyMainWindow()
@@ -462,18 +501,18 @@ QDockWidget *FancyMainWindow::addDockForWidget(QWidget *widget, bool immutable)
 
         dockWidget->setProperty(dockWidgetActiveState, true);
 
-        connect(dockWidget,
-                &QDockWidget::dockLocationChanged,
-                this,
-                &FancyMainWindow::dockWidgetsChanged);
-        connect(dockWidget,
-                &QDockWidget::topLevelChanged,
-                this,
-                &FancyMainWindow::dockWidgetsChanged);
-        connect(dockWidget,
-                &QDockWidget::visibilityChanged,
-                this,
-                &FancyMainWindow::dockWidgetsChanged);
+        const auto handleDockWidgetChanged = [this, dockWidget] {
+            // If the dock moved to an area that was hidden, unhide the area.
+            const Qt::DockWidgetArea area = dockWidgetArea(dockWidget);
+            if (dockWidget->isVisible() && !dockWidget->isFloating()
+                && d->m_hiddenAreas.contains(area)) {
+                setDockAreaVisible(area, true);
+            }
+            emit dockWidgetsChanged();
+        };
+        connect(dockWidget, &QDockWidget::dockLocationChanged, this, handleDockWidgetChanged);
+        connect(dockWidget, &QDockWidget::topLevelChanged, this, handleDockWidgetChanged);
+        connect(dockWidget, &QDockWidget::visibilityChanged, this, handleDockWidgetChanged);
     }
 
     return dockWidget;
@@ -547,6 +586,7 @@ QHash<Key, QVariant> FancyMainWindow::saveSettings() const
         settings.insert(keyFromString(dockWidget->objectName()),
                 dockWidget->property(dockWidgetActiveState));
     }
+    settings.insert(HiddenDockAreasKey, d->hiddenDockAreasToHash());
     return settings;
 }
 
@@ -562,6 +602,7 @@ void FancyMainWindow::restoreSettings(const QHash<Key, QVariant> &settings)
         widget->setProperty(dockWidgetActiveState,
                             settings.value(keyFromString(widget->objectName()), false));
     }
+    d->restoreHiddenDockAreasFromHash(settings.value(HiddenDockAreasKey).toHash());
 }
 
 bool FancyMainWindow::restoreFancyState(const QByteArray &state, int version)
@@ -592,6 +633,13 @@ const QList<QDockWidget *> FancyMainWindow::dockWidgets() const
     return result;
 }
 
+QList<QDockWidget *> FancyMainWindow::docksInArea(Qt::DockWidgetArea area) const
+{
+    return filtered(dockWidgets(), [this, area](QDockWidget *w) {
+        return w->isVisible() && !w->isFloating() && dockWidgetArea(w) == area;
+    });
+}
+
 bool FancyMainWindow::isCentralWidgetShown() const
 {
     return d->m_showCentralWidget.isChecked();
@@ -602,6 +650,37 @@ void FancyMainWindow::showCentralWidget(bool on)
     d->m_showCentralWidget.setChecked(on);
 }
 
+void FancyMainWindow::setDockAreaVisible(Qt::DockWidgetArea area, bool visible)
+{
+    if (visible) {
+        const QList<QDockWidget *> docks = d->m_hiddenAreas.value(area);
+        for (QDockWidget *w : docks)
+            w->setVisible(true);
+        d->m_hiddenAreas.remove(area);
+    } else {
+        const QList<QDockWidget *> docks = docksInArea(area);
+        if (!docks.isEmpty()) {
+            d->m_hiddenAreas.insert(area, docks);
+            for (QDockWidget *w : docks)
+                w->setVisible(false);
+        }
+    }
+}
+
+bool FancyMainWindow::isDockAreaVisible(Qt::DockWidgetArea area) const
+{
+    if (d->m_hiddenAreas.contains(area))
+        return false;
+    return !docksInArea(area).isEmpty();
+}
+
+bool FancyMainWindow::isDockAreaAvailable(Qt::DockWidgetArea area) const
+{
+    if (d->m_hiddenAreas.contains(area))
+        return true;
+    return !docksInArea(area).isEmpty();
+}
+
 void FancyMainWindow::addDockActionsToMenu(QMenu *menu)
 {
     QList<QAction *> actions;
diff --git a/src/libs/utils/fancymainwindow.h b/src/libs/utils/fancymainwindow.h
index df9f2c1281e..3762b7b6e5e 100644
--- a/src/libs/utils/fancymainwindow.h
+++ b/src/libs/utils/fancymainwindow.h
@@ -26,6 +26,7 @@ public:
      * which will then be used as key for QSettings. */
     QDockWidget *addDockForWidget(QWidget *widget, bool immutable = false);
     const QList<QDockWidget *> dockWidgets() const;
+    QList<QDockWidget *> docksInArea(Qt::DockWidgetArea area) const;
 
     void setTrackingEnabled(bool enabled);
 
@@ -44,6 +45,10 @@ public:
     bool isCentralWidgetShown() const;
     void showCentralWidget(bool on);
 
+    void setDockAreaVisible(Qt::DockWidgetArea area, bool visible);
+    bool isDockAreaVisible(Qt::DockWidgetArea area) const;
+    bool isDockAreaAvailable(Qt::DockWidgetArea area) const;
+
 signals:
     // Emitted by resetLayoutAction(). Connect to a slot
     // restoring the default layout.
diff --git a/src/plugins/coreplugin/designmode.cpp b/src/plugins/coreplugin/designmode.cpp
index 3b5e5fa41f7..728edc25dc0 100644
--- a/src/plugins/coreplugin/designmode.cpp
+++ b/src/plugins/coreplugin/designmode.cpp
@@ -14,6 +14,10 @@
 
 #include <extensionsystem/pluginmanager.h>
 
+#include <utils/fancymainwindow.h>
+
+#include <aggregation/aggregate.h>
+
 #include <QDebug>
 #include <QPointer>
 #include <QStackedWidget>
@@ -198,6 +202,11 @@ void DesignMode::setActiveContext(const Context &context)
     d->m_activeContext = context;
 }
 
+Utils::FancyMainWindow *DesignMode::mainWindow()
+{
+    return Aggregation::query<Utils::FancyMainWindow>(d->m_stackWidget->currentWidget());
+}
+
 void DesignMode::createModeIfRequired()
 {
     if (d) {
diff --git a/src/plugins/coreplugin/designmode.h b/src/plugins/coreplugin/designmode.h
index da9a6f70ab6..82b00abb2b6 100644
--- a/src/plugins/coreplugin/designmode.h
+++ b/src/plugins/coreplugin/designmode.h
@@ -44,6 +44,8 @@ private:
     void currentEditorChanged(IEditor *editor);
     void updateContext(Utils::Id newMode, Utils::Id oldMode);
     void setActiveContext(const Context &context);
+
+    Utils::FancyMainWindow *mainWindow() override;
 };
 
 } // namespace Core
diff --git a/src/plugins/coreplugin/icore.cpp b/src/plugins/coreplugin/icore.cpp
index 354ce144e13..ca92b3b9c6c 100644
--- a/src/plugins/coreplugin/icore.cpp
+++ b/src/plugins/coreplugin/icore.cpp
@@ -1343,8 +1343,7 @@ NavigationWidget *ICorePrivate::navigationWidget(Side side) const
 
 void ICorePrivate::setSidebarVisible(bool visible, Side side)
 {
-    if (NavigationWidgetPlaceHolder::current(side))
-        navigationWidget(side)->setShown(visible);
+    navigationWidget(side)->setShown(visible);
 }
 
 ICorePrivate::~ICorePrivate()
diff --git a/src/plugins/coreplugin/imode.cpp b/src/plugins/coreplugin/imode.cpp
index 4cd530280ca..f143459cf6b 100644
--- a/src/plugins/coreplugin/imode.cpp
+++ b/src/plugins/coreplugin/imode.cpp
@@ -5,6 +5,10 @@
 
 #include "modemanager.h"
 
+#include <utils/fancymainwindow.h>
+
+#include <aggregation/aggregate.h>
+
 namespace Core {
 
 /*!
@@ -111,6 +115,11 @@ void IMode::setEnabled(bool enabled)
     emit enabledStateChanged(m_isEnabled);
 }
 
+Utils::FancyMainWindow *IMode::mainWindow()
+{
+    return Aggregation::query<Utils::FancyMainWindow>(widget());
+}
+
 bool IMode::isEnabled() const
 {
     return m_isEnabled;
diff --git a/src/plugins/coreplugin/imode.h b/src/plugins/coreplugin/imode.h
index 0cdedd9bacf..339d0ccf84a 100644
--- a/src/plugins/coreplugin/imode.h
+++ b/src/plugins/coreplugin/imode.h
@@ -10,6 +10,10 @@
 #include <QIcon>
 #include <QMenu>
 
+namespace Utils {
+class FancyMainWindow;
+}
+
 namespace Core {
 
 class CORE_EXPORT IMode : public IContext
@@ -39,6 +43,8 @@ public:
     void setId(Utils::Id id) { m_id = id; }
     void setMenu(QMenu *menu) { m_menu = menu; }
 
+    virtual Utils::FancyMainWindow *mainWindow();
+
 signals:
     void enabledStateChanged(bool enabled);
 
diff --git a/src/plugins/coreplugin/navigationwidget.cpp b/src/plugins/coreplugin/navigationwidget.cpp
index d2b1dafcd51..b6961f8612a 100644
--- a/src/plugins/coreplugin/navigationwidget.cpp
+++ b/src/plugins/coreplugin/navigationwidget.cpp
@@ -7,16 +7,22 @@
 #include "coreplugintr.h"
 #include "icontext.h"
 #include "icore.h"
+#include "imode.h"
 #include "inavigationwidgetfactory.h"
 #include "modemanager.h"
 #include "navigationsubwidget.h"
 
+#include <utils/algorithm.h>
+#include <utils/fancymainwindow.h>
 #include <utils/qtcassert.h>
 #include <utils/utilsicons.h>
 
+#include <aggregation/aggregate.h>
+
 #include <QAction>
 #include <QCoreApplication>
 #include <QDebug>
+#include <QDockWidget>
 #include <QHBoxLayout>
 #include <QResizeEvent>
 #include <QStandardItemModel>
@@ -107,7 +113,7 @@ void NavigationWidgetPlaceHolder::currentModeAboutToChange(Id mode)
         setCurrent(m_side, nullptr);
         navigationWidget->setParent(nullptr);
         navigationWidget->hide();
-        navigationWidget->placeHolderChanged(nullptr);
+        navigationWidget->placeHolderChanged();
     }
 
     if (m_mode == mode) {
@@ -118,7 +124,7 @@ void NavigationWidgetPlaceHolder::currentModeAboutToChange(Id mode)
 
         applyStoredSize();
         setVisible(navigationWidget->isShown());
-        navigationWidget->placeHolderChanged(this);
+        navigationWidget->placeHolderChanged();
     }
 }
 
@@ -142,6 +148,7 @@ struct NavigationWidgetPrivate
     QHash<QAction *, Id> m_actionMap;
     QHash<Id, Command *> m_commandMap;
     QStandardItemModel *m_factoryModel;
+    FancyMainWindow *m_mainWindow = nullptr;
 
     bool m_shown;
     int m_width;
@@ -185,6 +192,11 @@ NavigationWidget::NavigationWidget(QAction *toggleSideBarAction, Side side) :
         NavigationWidgetPrivate::s_instanceLeft = this;
     else
         NavigationWidgetPrivate::s_instanceRight = this;
+
+    connect(ModeManager::instance(),
+            &ModeManager::currentModeChanged,
+            this,
+            &NavigationWidget::updateMode);
 }
 
 NavigationWidget::~NavigationWidget()
@@ -243,7 +255,7 @@ void NavigationWidget::setFactories(const QList<INavigationWidgetFactory *> &fac
         d->m_factoryModel->appendRow(newRow);
     }
     d->m_factoryModel->sort(0);
-    updateToggleText();
+    updateToggleAction();
 }
 
 Key NavigationWidget::settingsGroup() const
@@ -261,23 +273,41 @@ QAbstractItemModel *NavigationWidget::factoryModel() const
     return d->m_factoryModel;
 }
 
-void NavigationWidget::updateToggleText()
+void NavigationWidget::updateMode()
 {
-    bool haveData = d->m_factoryModel->rowCount();
-    d->m_toggleSideBarAction->setVisible(haveData);
-    d->m_toggleSideBarAction->setEnabled(haveData && NavigationWidgetPlaceHolder::current(d->m_side));
+    IMode *currentMode = ModeManager::currentMode();
+    FancyMainWindow *mainWindow = currentMode ? currentMode->mainWindow() : nullptr;
+    if (d->m_mainWindow == mainWindow)
+        return;
+    if (d->m_mainWindow)
+        disconnect(d->m_mainWindow, nullptr, this, nullptr);
+    d->m_mainWindow = mainWindow;
+    if (d->m_mainWindow)
+        connect(d->m_mainWindow,
+                &FancyMainWindow::dockWidgetsChanged,
+                this,
+                &NavigationWidget::updateToggleAction);
+    updateToggleAction();
+}
 
-    const char *trToolTip = d->m_side == Side::Left
-                                ? (isShown() ? Constants::TR_HIDE_LEFT_SIDEBAR : Constants::TR_SHOW_LEFT_SIDEBAR)
-                                : (isShown() ? Constants::TR_HIDE_RIGHT_SIDEBAR : Constants::TR_SHOW_RIGHT_SIDEBAR);
+void NavigationWidget::updateToggleAction()
+{
+    d->m_toggleSideBarAction->setVisible(toggleActionVisible());
+    d->m_toggleSideBarAction->setEnabled(toggleActionEnabled());
+    d->m_toggleSideBarAction->setChecked(toggleActionChecked());
+    const char *trToolTip = d->m_side == Side::Left ? (d->m_toggleSideBarAction->isChecked()
+                                                           ? Constants::TR_HIDE_LEFT_SIDEBAR
+                                                           : Constants::TR_SHOW_LEFT_SIDEBAR)
+                                                    : (d->m_toggleSideBarAction->isChecked()
+                                                           ? Constants::TR_HIDE_RIGHT_SIDEBAR
+                                                           : Constants::TR_SHOW_RIGHT_SIDEBAR);
 
     d->m_toggleSideBarAction->setToolTip(Tr::tr(trToolTip));
 }
 
-void NavigationWidget::placeHolderChanged(NavigationWidgetPlaceHolder *holder)
+void NavigationWidget::placeHolderChanged()
 {
-    d->m_toggleSideBarAction->setChecked(holder && isShown());
-    updateToggleText();
+    updateToggleAction();
 }
 
 void NavigationWidget::resizeEvent(QResizeEvent *re)
@@ -376,6 +406,37 @@ void NavigationWidget::closeSubWidget(Internal::NavigationSubWidget *subWidget)
     }
 }
 
+bool NavigationWidget::toggleActionVisible() const
+{
+    const bool haveData = d->m_factoryModel->rowCount();
+    return haveData || d->m_mainWindow;
+}
+
+static Qt::DockWidgetArea dockAreaForSide(Side side)
+{
+    return side == Side::Left ? Qt::LeftDockWidgetArea : Qt::RightDockWidgetArea;
+}
+
+bool NavigationWidget::toggleActionEnabled() const
+{
+    const bool haveData = d->m_factoryModel->rowCount();
+    if (haveData && NavigationWidgetPlaceHolder::current(d->m_side))
+        return true;
+    if (!d->m_mainWindow)
+        return false;
+    return d->m_mainWindow->isDockAreaAvailable(dockAreaForSide(d->m_side));
+}
+
+bool NavigationWidget::toggleActionChecked() const
+{
+    const bool haveData = d->m_factoryModel->rowCount();
+    if (haveData && NavigationWidgetPlaceHolder::current(d->m_side))
+        return d->m_shown;
+    if (!d->m_mainWindow)
+        return false;
+    return d->m_mainWindow->isDockAreaVisible(dockAreaForSide(d->m_side));
+}
+
 static QString defaultFirstView(Side side)
 {
     return side == Side::Left ? QString("Projects") : QString("Outline");
@@ -498,19 +559,22 @@ void NavigationWidget::closeSubWidgets()
 
 void NavigationWidget::setShown(bool b)
 {
-    if (d->m_shown == b)
-        return;
-    bool haveData = d->m_factoryModel->rowCount();
-    d->m_shown = b;
     NavigationWidgetPlaceHolder *current = NavigationWidgetPlaceHolder::current(d->m_side);
-    if (current) {
-        bool visible = d->m_shown && haveData;
-        current->setVisible(visible);
-        d->m_toggleSideBarAction->setChecked(visible);
+    if (!current && d->m_mainWindow) {
+        // mode without placeholder but with main window
+        d->m_mainWindow->setDockAreaVisible(dockAreaForSide(d->m_side), b);
     } else {
-        d->m_toggleSideBarAction->setChecked(false);
+        // mode with navigation widget placeholder or e.g. during startup/settings restore
+        if (d->m_shown == b)
+            return;
+        const bool haveData = d->m_factoryModel->rowCount();
+        d->m_shown = b;
+        if (current) {
+            const bool visible = d->m_shown && haveData;
+            current->setVisible(visible);
+        }
     }
-    updateToggleText();
+    updateToggleAction();
 }
 
 bool NavigationWidget::isShown() const
diff --git a/src/plugins/coreplugin/navigationwidget.h b/src/plugins/coreplugin/navigationwidget.h
index 40ea1a5fa0c..c043456b6ae 100644
--- a/src/plugins/coreplugin/navigationwidget.h
+++ b/src/plugins/coreplugin/navigationwidget.h
@@ -86,7 +86,7 @@ public:
     int storedWidth();
 
     // Called from the place holders
-    void placeHolderChanged(NavigationWidgetPlaceHolder *holder);
+    void placeHolderChanged();
 
     QHash<Utils::Id, Command *> commandMap() const;
     QAbstractItemModel *factoryModel() const;
@@ -96,7 +96,11 @@ protected:
 
 private:
     void closeSubWidget(Internal::NavigationSubWidget *subWidget);
-    void updateToggleText();
+    bool toggleActionVisible() const;
+    bool toggleActionEnabled() const;
+    bool toggleActionChecked() const;
+    void updateMode();
+    void updateToggleAction();
     Internal::NavigationSubWidget *insertSubItem(int position,
                                                  int factoryIndex,
                                                  bool updateActivationsMap = true);
diff --git a/src/plugins/designer/formeditor.cpp b/src/plugins/designer/formeditor.cpp
index 205c6120a82..57075e7ecc2 100644
--- a/src/plugins/designer/formeditor.cpp
+++ b/src/plugins/designer/formeditor.cpp
@@ -33,6 +33,8 @@
 #include <utils/stringutils.h>
 #include <utils/theme/theme.h>
 
+#include <aggregation/aggregate.h>
+
 #include <QDesignerFormEditorPluginInterface>
 #include <QDesignerFormEditorInterface>
 #include <QDesignerComponents>
@@ -405,6 +407,10 @@ void FormEditorData::fullInit()
 
     m_modeWidget = new QWidget;
     m_modeWidget->setObjectName("DesignerModeWidget");
+    // make the editor widget (the dockable widget) accessible via the mode widget
+    auto agg = new Aggregation::Aggregate;
+    agg->add(m_modeWidget);
+    agg->add(m_editorWidget);
     auto layout = new QVBoxLayout(m_modeWidget);
     layout->setContentsMargins(0, 0, 0, 0);
     layout->setSpacing(0);