Specifies if the navigation panel is expanded when the application is started in the new web UI.
true, if the navigation panel is initially expanded; otherwise, false.
The ShowNavigationOnStart property can be used to hide the navigation pane when it is displayed side by side with the View area.
The ShowNavigationOnStart property has no effect when the page width is less than 1000 pixels. In this instance, the navigation is located on a collapsible side panel which is always hidden by default, and which hovers the page content when the ☰ button is clicked.