A couple of idea: 1) Instead of creating a new ToolbarItem as separator, put your separator on the right and/or left of the previous/next ToolbarItem 2) Manage the toolbar by your own StackPanel
Personally I think you would be better of not using the Toolbar, but instead just put a set of buttons in a stackpanel., It's more flexible, more customizable and way simpler than using the Toolbar.