Comment 15 for bug 1430571

I'm runnin version 16.04 XCFE 4.12 distributed by XUBUNTU.

I had the same issues with the disappearing menu items after I had changed a few items such as installing GNURadio,Python, QT-5, Kicad and other applications such as the Libre Office Suite.

Then most of the menu items vanished to just a few default items such as system utilities Very few applications remained. They showed up in the software loader as installed but not in any menus.

Application Categories were gone as well.

FIX:
Used Panel editor to apply the fix as posted above by-
(Jon Holstrom (7-jon-r) wrote on 2016-06-27:) with one exception.

Loaded the original package menu file from "/etc/xdg/menus/xfce-applications.menu"
It loaded all of the UBUNTU STUDIO package menu categories and all additional applications were also shown in the menu.