@anon94368460 - this works really well! Very nice!
Maybe a screenshot can help:
A small change I made was that instead of reusing the /usr/lib/mate-menu directory (which already has the Advanced MATE Menu loader in it), I created a /usr/lib/mate-desktop-icons directory for my executable (and updated the path in the other two files accordingly).
After that, depending on your configuration, you might need to restart the panel (often killall mate-panel is all you need, as it will auto-restart) and then the applet will show up.
What I like the most about this is how easy it is to get started - this can be used as a template for others to create whatever applet they want, and it just works!