I have the Compatibility Files toggle button on my File Display Toolbar. In customization mode, the icon shows in both lister panes (two pane with tree layout), and when you move the position of one, they both move - which is fine. But when you go back to the normal view, the button only shows up in the right pane. No button in the left pane.
If I create a second button, and put it in the left pane, when I close customization, I get two buttons in the right pane.