The FXDesktopPane supports window manager. The standard window manager shows multiple windows on the desktop and handles global windows.

It's also possible to set a window manager for single-window mode. This window manager shows the content as maximized window:

desktopPane.setWindowManager(new FXGlobalModalWindowManager(new FXSingleWindowManager()));

If you don't need support for global windows:

desktopPane.setWindowManager(new FXSingleWindowManager());