I'm finally getting around to trying your solution, Guy, and it does not work. I've double- and triple-checked spelling, paths, existence of newly-created directories, and so on. There is no origtce.wbar in /usr/local, for one thing. So that part's not working. Furthermore, /usr/local/tce.wbar does not match /home/tc/.mymenu/wbar/tce.wbar, so that part's not working either. mv /home/tc/.wmx /tmp/.origwmx seems to be about the only part of this routine that works, since I do find a /.origwmx in /tmp. But what's in /home/tc/.wmx does not match the content of /home/tc/.mymenu/.wmx, so that part doesn't work either.
Thus, my original question still stands: how can I modify, such that it survives reboots, wbar and the pop-up menu that appears when you click on the background? For this distro to be a multi-user system (one where you don't want all users to be able to fiddle with important system files and settings), this sort of thing has to made more straightforward. As it stands I'm stuck trying to reverse-engineer the way the system has been set up to function.
James