Here is the fix :
Xubuntu system menu items are controlled via files in the following directory :
This directory contains a lot of files that end in .desktop
These are the files that control what menu items appear in certain categories.
- Open the .desktop file of the menu item you want to add to a catagory ( file A )
- Open the .desktop file of a menu item already in that category ( file B )
- Replace the "Categories=" line in file A with the one from file B.
You may have to restart XFCE for the changes to show up or perform some action that requires the menu file to be reloaded ( like check the check "hidden" for something in the menu editor then hit save ).
If there is no .desktop file for the program you want to add then create a new file (make sure it ends in .desktop) and copy the contents from a file in that catagory into your new file.
Then change all the important details and everything should work.
To open the .desktop file as root go to a root terminal and inside the
/usr/share/applications directory and execute :
Or from the regular terminal inside the
/usr/share/applications directory execute
"sudo mousepad filename.desktop"