From a user in the AppMenu survey:
“Most of my menu interaction is with xfce launchers on the taskbar, one for each of my most used qubes.”
^^ How can I do this??? I want to learn more! And no, this user did not include their email address for a follow-up. 
I guess:
Qubes Menu > System tools > Panel > items > + > launcher
then you can edit the launcher a put there some app. It makes easier to get the most used apps right there, just one click apart.
Another way and more details:
Right-click on taskbar > Panel > Add New Items… > Launcher > + Add > Close
Then an empty blind launcher added on the most right part of the taskbar (after the user account).
Right click on that new launcher > Properties > + > choose your wanted application from AppVMs.
Right click on that new launcher > - Remove
Right click on that new launcher > → Move
In general, in the taskbar, I move my launchers on the left of the Workspace Switcher.