When we right click the main menu on the panel we get some options. Is it possible to remove Edit Menus option from that?
Okay, this doesn't remove the menu entry, but it makes it useless, should be just what you need:
First, make a backup copy of alacarte, the menu editor:
Now open up the original in your favourite text editor:
In between the end of the big comment on the top and the line that says
You can of course replace "Not Allowed" with any error message you like.
Now when you click "edit menus", this message will pop up:
Of course this is not 'secure', a knowledgeable user will be able to get around it, but I guess that's fine in your case. I also haven't tested if any other applications break because of it, but looking at the code, that shouldn't happen.
Note: if you want to use an error message consisting of characters outside of ASCII, make sure the it says
Stefano and I have been talking about this in Chat today. I think he's working on another direction, but I've got a couple of source-based ways to work around this.