The switch was just put in for a month or so around sept/oct 2015
I don't have the switch (build date July 2015) and units in November 2015 don't have one.
The wire is just a hot lead behind the centre light. I couldn't find it when I installed my wired camera on the back, but I wasn't concerned because the wiring harness for the camera had power already. Then I installed my own lighted switch in the leveling controller compartment.
Here's the thread of the mod if you're interested
If you really want to put a switch in, and use the "prewire" I might be able to help. You would have to test it on your rig, because I couldn't find the wire to test it myself.