Currently there is no event or public means to manipulate this list. The default template for the TabGroupPane contains a menu item (named PART_FilesMenuItem). When the menu item is opened, the tabgrouppane clears it and adds in a menuitem for each visible pane. You should submit a suggestion for adding an event for this menu similar to how the ContentPane raises an event for its options menu. For now, you would probably need to retemplate the tabgrouppane, not include that PART_FilesMenuItem and instead add in your own custom control or menu and populate it as required.