I would like to be able to set the juke box to automatically switch to the next demo folder and keep playing one folder after another in numerical order. Would like to be able to set it forward and reverse. I could then set it to play for hours while I'm doing other work and not have to keep changing the folder to get to a new set of demos.

No can do. Works on a single folder at a time. May want to put this in the Wish List.

Er, I think he did (!)

Indeed he did!
There are however some other niggles I have with that whole set of Jukebox features, particularly those regarding soloist and RT's (which simply don't work together!).
So if this increases the chances of PG's overhaul of that whole section, then a +1.