I do not have a switch panel like that. The 2 slides are separate buttons, and the other separate switch is the outside curbside light. Those 3 switches are on the upper cabinet above the sink, right by the door.
The water heater switch is on the cabinet below the sink, the water pump switch and black/grey water levels control is in the bathroom.
If it makes you feel better our unit has (1) scare light on each side and we (Never)use them! I (Gutted) the one on the Door side and used it for a weatherproof area to mount the Box for (LED Awning Lights) and the switch is on a Panel at the door. Youroo!!
OP, I am 99.9% sure this is not a factory light (scare, spot, whatever you want to call it). It would have been something the previous owner added. What is directly behind the light on the inside? They had to pull power from somplace, and chances are the switch is close to that source.
I added a exterior switched light (swithc on the light housing) on the hookup/road side of my unit for night time setup.