Added a 'Float All' menu item to tabbed MDI tabs, which floats all docking windows in the container together.
Improved the target dock host hit-test logic.
Improved focus tracking related to WebView2 controls.
Increased the default TabbedMdiHost.MaxTabExtent width, and added remarks to its API documentation.
Updated tool window-only layout deserializations to not clear lazy-load data for document windows.
Editors
Added the AutoCompleteBox.PopupHeader, PopupHeaderTemplate, and PopupHeaderTemplateSelector properties that allow for injecting a header above the popup's suggestion list.
Ribbon
Updated the small/medium variant SplitButton template to better support a large CornerRadius setting.
Consolidated usage of SystemParameters.IsMenuDropRightAligned to use MenuDropAlignment instead.
Themes
Updated the Theme Designer app's Base Color Finder tool to support dark themes.
Updated WindowChrome shadow positioning logic when dealing with multiple monitors that have different DPIs.
Updated the custom-rendered WindowChrome shadow to not be included in screen captures.
Updated menu item templates to make use of a new ResizablePopupContentHost primitive.
Shared
Added the PopupButton.CornerRadius property.
Updated how CanvasControl handles rendering transparent colors.