Gets or sets whether the current item is marked as favorite in the sub-menu fly-out panel when it is assigned to be displayed in the preview.
true, to show the mark indicating that the current item is favorite and also displayed in the preview; otherwise, false. The default is true.
If the HamburgerSubMenuNavigationButton.ShowInPreview property is set to true, the current item is displayed directly in the main menu in the preview. If this option is enabled, the current item is marked as favorite in the sub-menu fly-out panel indicating that the current item is also displayed in the preview. Set the ShowPreviewMark property to false, to hide this mark.