Window Confinement Region
The Window Confinement Region contains open Source, User Interface Editor, Function Panel Editor, and Function Tree Editor windows and function panels. When you open any of these windows, the menu and toolbar change to reflect new options in those windows. You can release windows from the Window Confinement Region by selecting Window»Release Window.
By default, windows appear in tabs in the Window Confinement Region. If you want to minimize or maximize windows within the Window Confinement Region, disable the Show tabbed Workspace option in the Environment dialog box.