What desktop environment or window manager are you using? Each one has a slightly different way of editing the menu.
In Gnome or KDE, right clicking over the show menu icon usually throws up a menu which includes an option to edit the menu; both of them also have "edit menu" functions in buried in their regular menus
(I say "usually" because I don't use either one regularly--I usually use Fluxbox
). It does everything I want without any extraneous hockeypuck.)
If you are using a window manager, such as Fluxbox, try going to the main page for the window manager you are using and searching for "edit menu" or something like that or giggle for "edit menu [window manager name]."