Specifies whether the `VisualElement` for this toolbar element should be displayed or not. Set to `True` by default.
This displayed state applies to the `VisualElement` of the toolbar element. To display the visual content when you add a toolbar element to the toolbar set this field to `True`. Set this field to `False` to hide the visual content so that the element doesn't take up any space in the toolbar. This is `True` by default.