As long as I understand - menu in xfce is just an xml file.
One can write whatever is necessary in it.
For example I have made my own menu and place it next to original, when I click its icon I
see only
what I added.
When click right mouse button on "application menu" icon there is the option
"use the default menu
file" or "use custom menu file". Copy original file to home directory and
play with it with "Geany".
Thanks.