Hi Jeff, welcome to the club.
I'll take a shot at your mystery toggle switch. I am assuming it is a momentary switch.
The previous owner most likely had Henderson's Line Up in Grants Pass, Oregon or another RV Chassis expert in another state install a "SAFE-T-PLUS" by SuperSteer steering control on your unit. It operates similar to other steering control units and yours may be a different brand.
The way mine works is when driving, position the wheel on a path that will keep you in the middle of your lane. Toggle the switch to the momentary position and hold for a couple of seconds and then release. If done properly you will traverse down the road without hardly any deviation of the steering wheel, I can actually take my hands of the wheel and it will stay in my lane. It is especially nice when you have a strong crosswind or a lot of trucks passing you at high speed. I just drove across Alberta and Manitoba on 16 and 1 with heavy crosswind and it was a breeze (except for crappy roads and RR tracks at 65MPH).
I had Henderson's install mine this spring and the difference in driver fatigue is amazing. After 5,500 miles my feeling is I wish I would have installed it 10 years ago. If the previous owner installed this option check for Koni shocks and SuperSteer Motion Control Unit.
The web site is:
www.SuperSteerParts.comLook under the coach at the steering arms and check for what looks like a big shock with air assist.