@whale-av For this test, I was using Windows (my main machine is Linux, though).
I eventually found the home/.vstplugin~/cache.ini file, and it does contain not only the list of plugins, but also the list of programs. Cleared that, rescanned, and it picked up the new items right away.
I'll check again for a command to make it clear the cache. Students won't like it if the story is "after you save a preset in the VST, you have to find this hidden folder and delete a file, and rescan. Possibly I just overlooked it.
Christof did some bang-up work on this object btw... Software integration usually brings headaches, but vstplugin~ was able to find and use Helm cleanly. When the hardest part of it is figuring out which commands to use (vs dealing with random crashes or garbled output or whatever), that's a good place to be.