This release introduces a new context menu type for desktop apps that can overflow the parent window:

Code snippet:
<TextBlock Text="Right click on me to show the context menu">
<multiwindow:ContextMenuService.ContextMenu>
<multiwindow:ContextMenuWindow>
<multiwindow:MenuItem Header="Menu Item"/>
</multiwindow:ContextMenuWindow>
</multiwindow:ContextMenuService.ContextMenu>
</TextBlock>