This looked like a cool idea.
It has been implemented in the current ArcoLinux.
We need to navigate to /usr/share/applications and open one of the .desktop files in there to see why they are included or excluded from xfce settings.
Experiment using sublime text. It will let you save with a popup to fill out your root password.
Now you can add any application to your xfce settings manager.
The categories line in the .desktop files decides if your icon (shortcut) will show up or not.