I wouldn't lose any sleep over this. The manufacturer of the pads now says that no damage will be done to any tank, they just suggest they be turned off when not needed so the pads don't cycle on and off unnecessarily.
Probably should be labeled but not surprising if not. If you can access the tanks a simple check with test light or Multi-Meter can ID which switch controls which heater pad. THEN label the switches.
Pads are supposed to shut off at 60 degrees as temp rises. Wattage is low with most pads maxing out at 75 watts for the largest. Small pads for the elbows/pipes are a lot less at only 7 watts.
It's not as if you have an electric hotplate that's being left on without a pot of water on it.
FWIW, Forest River's "Manual" that they supply is both generic and outdated. Best information is from the accessory supplier's themselves by going to their websites. If the current manuals aren't posted most have a form under their "Contact Us" tab where you can ask a question and most will get back with an answer in a day or two.