If you are only interested in what controls what in the 12 volt
system. Then turn everything on and start by pulling one fuse at a time to see what goes off. Make a note of it.
As far as the 120 volt AC there are probably only 2 circuits; one to feed all of the outlets in the trailer including the refer. Another to power the Air Conditioner if you have one.
The exterior lighting would be easily checked out with a battery or a Battery charger. If all wires are connected to the umbilical cord, plug it in to the TV and check the various circuits out.