true, if the current sub menu item is shown as a preview directly in the main menu below the sub menu button; otherwise, false.
With the HamburgerSubMenu.Items collection, you specify items of the current sub menu. These items are displayed in the fly-out panel invoked by clicking or tapping the sub-menu button. It is also possible to display sub menu items directly in the main menu below the sub menu button, as a preview. To display a particular item in a preview, set its ShowInPreview property to true. See an example below.