I don't know what it does but it sounds like your dealer doesn't either. Whatever it does the dealer should have told you its purpose. It really surprises me how bad RV dealers are at explaining their products. Can you imagine how much more happy we would be if RV dealers cared about our satisfaction?
On my previous diesel motorhome the engine block heater switch was in the bedroom and had a red light when on. Use the heater in very cold (freezing) temperatures to heat the engine oil and make cold weather starting easier. It is powered by 120 volts.
Can't tell you what that is, but I suggest you call Thor and ask them. While you have them on the line, ask them to send you the schematics of the wiring, both 110 and 12v, and the plumbing. Then come back here and educate the group.
There are friends, there are family, and then there are friends that become family!