Today I had a few issues with finding the correct files for XFCE4 installed on an Ubuntu release. Due to Gnome being present all the existing menu editors assumed I use Gnome and were pretty much useless...
So basically, the files of importance:
Main Menu File:
All the .desktop files mentioned are in:
You can copy an existing .desktop and modify it to create a custom menu item then simply reference it in the correct file, mine were all in the main xfce-applications.menu file.