With the .XWinrc configuration file it is possible to:
Add items and submenus into the menu opened by right-clicking on the notification area icon.
In multiwindow mode: add items and submenus into the Windows window system menu (opened by clicking on the icon in the top-left of the Windows window frame) and override the window icon and window styles for Windows windows, by window name or window class name.
Full documentation of the XWinrc file format and command can be read with man XWinrc .