diff --git a/share/qtcreator/qmldesigner/materialEditorQmlSources/EmptyMaterialEditorPane.qml b/share/qtcreator/qmldesigner/materialEditorQmlSources/EmptyMaterialEditorPane.qml
index 355f71f7591..c8b2ab7ef6c 100644
--- a/share/qtcreator/qmldesigner/materialEditorQmlSources/EmptyMaterialEditorPane.qml
+++ b/share/qtcreator/qmldesigner/materialEditorQmlSources/EmptyMaterialEditorPane.qml
@@ -10,6 +10,9 @@ import StudioTheme 1.0 as StudioTheme
 PropertyEditorPane {
     id: root
 
+    width: 420
+    height: 420
+
     signal toolBarAction(int action)
     signal previewEnvChanged(string env)
     signal previewModelChanged(string model)
diff --git a/share/qtcreator/qmldesigner/materialEditorQmlSources/MaterialEditorPane.qml b/share/qtcreator/qmldesigner/materialEditorQmlSources/MaterialEditorPane.qml
index 52e49074483..0816d01ec4c 100644
--- a/share/qtcreator/qmldesigner/materialEditorQmlSources/MaterialEditorPane.qml
+++ b/share/qtcreator/qmldesigner/materialEditorQmlSources/MaterialEditorPane.qml
@@ -8,6 +8,9 @@ import HelperWidgets 2.0
 PropertyEditorPane {
     id: itemPane
 
+    width: 420
+    height: 420
+
     signal toolBarAction(int action)
     signal previewEnvChanged(string env)
     signal previewModelChanged(string model)
diff --git a/share/qtcreator/qmldesigner/textureEditorQmlSource/EmptyTextureEditorPane.qml b/share/qtcreator/qmldesigner/textureEditorQmlSource/EmptyTextureEditorPane.qml
index 9623232146b..70fa841461a 100644
--- a/share/qtcreator/qmldesigner/textureEditorQmlSource/EmptyTextureEditorPane.qml
+++ b/share/qtcreator/qmldesigner/textureEditorQmlSource/EmptyTextureEditorPane.qml
@@ -10,6 +10,9 @@ import StudioTheme 1.0 as StudioTheme
 PropertyEditorPane {
     id: root
 
+    width: 420
+    height: 420
+
     signal toolBarAction(int action)
 
     // Called from C++, dummy method to avoid warnings
diff --git a/share/qtcreator/qmldesigner/textureEditorQmlSource/TextureEditorPane.qml b/share/qtcreator/qmldesigner/textureEditorQmlSource/TextureEditorPane.qml
index 0aa6bd4e093..2098eda5165 100644
--- a/share/qtcreator/qmldesigner/textureEditorQmlSource/TextureEditorPane.qml
+++ b/share/qtcreator/qmldesigner/textureEditorQmlSource/TextureEditorPane.qml
@@ -8,6 +8,9 @@ import HelperWidgets 2.0
 PropertyEditorPane {
     id: itemPane
 
+    width: 420
+    height: 420
+
     signal toolBarAction(int action)
 
     // invoked from C++ to refresh material preview image
diff --git a/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.cpp b/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.cpp
index 1b5bdb8c768..cf968a33a89 100644
--- a/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.cpp
+++ b/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.cpp
@@ -596,6 +596,11 @@ void ContentLibraryWidget::markTextureUpdated(const QString &textureKey)
         m_environmentsModel->markTextureHasNoUpdates(subcategory, textureKey);
 }
 
+QSize ContentLibraryWidget::sizeHint() const
+{
+    return {420, 420};
+}
+
 QList<QToolButton *> ContentLibraryWidget::createToolBarWidgets()
 {
     return {};
diff --git a/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.h b/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.h
index a5baa66dd1c..5e41f289141 100644
--- a/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.h
+++ b/src/plugins/qmldesigner/components/contentlibrary/contentlibrarywidget.h
@@ -71,6 +71,8 @@ public:
     Q_INVOKABLE void updateSceneEnvState();
     Q_INVOKABLE void markTextureUpdated(const QString &textureKey);
 
+    QSize sizeHint() const override;
+
 signals:
     void bundleEffectDragStarted(QmlDesigner::ContentLibraryEffect *bundleEff);
     void bundleMaterialDragStarted(QmlDesigner::ContentLibraryMaterial *bundleMat);
diff --git a/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.cpp b/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.cpp
index 02fe24e344c..25df13603b9 100644
--- a/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.cpp
+++ b/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.cpp
@@ -109,6 +109,11 @@ void EffectMakerWidget::focusSection(int section)
     Q_UNUSED(section)
 }
 
+QSize EffectMakerWidget::sizeHint() const
+{
+    return {420, 420};
+}
+
 QString EffectMakerWidget::qmlSourcesPath()
 {
 #ifdef SHARE_QML_PATH
diff --git a/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.h b/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.h
index e42edd04400..74780425aef 100644
--- a/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.h
+++ b/src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.h
@@ -38,6 +38,8 @@ public:
     Q_INVOKABLE void addEffectNode(const QString &nodeQenPath);
     Q_INVOKABLE void focusSection(int section);
 
+    QSize sizeHint() const override;
+
 protected:
     bool eventFilter(QObject *obj, QEvent *event) override;
 
diff --git a/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.cpp b/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.cpp
index 98a1a5a5def..47a1e8d293e 100644
--- a/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.cpp
+++ b/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.cpp
@@ -405,6 +405,11 @@ void MaterialBrowserWidget::clearPreviewCache()
     m_previewImageProvider->clearPixmapCache();
 }
 
+QSize MaterialBrowserWidget::sizeHint() const
+{
+    return {420, 420};
+}
+
 QPointer<MaterialBrowserModel> MaterialBrowserWidget::materialBrowserModel() const
 {
     return m_materialBrowserModel;
diff --git a/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.h b/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.h
index ea0e5a212ab..bfe7ace34d6 100644
--- a/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.h
+++ b/src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.h
@@ -65,6 +65,8 @@ public:
 
     void clearPreviewCache();
 
+    QSize sizeHint() const override;
+
 signals:
     void materialSectionFocusedChanged();
     void isDraggingChanged();