Hi and welcome to the forums! Sorry that I can't answer your question but I found a variety of answers when I did a quick search from the cabinet in the bathroom, panel above the fridge, to outside by the p-tanks just to list a few locations.
Hopefully someone soon will drop by or that someone that has the same unit will know.
You mentioned that above the panel, there is an unmarked switch. Are you able to post a picture of it? Doing so might yield an answer quicker but no promises.
Great choice for "Living within my means" and camping for one...
2011 Salem Cruise Lite 20RBXL & 2011 Toyota Tundra Dbl Cab
Camping History: 45 Trips / 133 Nights / 3736 Miles
FRF Social Group: Campers of the West