Behind the headlight I found a 2 pin white plug with 3 yellow/red wires and a black wire. The plug is hanging free. I think I found it in the wiring diagram. As the diagram shows, the black wire is ground and one yellow/red wire goes to the ignition switch, the second to the tail light, and a third to a dashboard plug (not shown below). I can't figure out what it does and what it should be plug into. Everything seems to work on the bike.

It's the small 5w parking lamp. It is certainly found in European and Australian models but may not be universal. The parking circuit is energised when the ignition key is taken past the steering lock and the key removed.
Cheers Willo
Wannon Australia

Yep, I just found reference to it in the workshop manual as you were posting. That is not a feature in the US. I can see through the lens a place where that bulb would have been. It is blocked off. Another mystery solved. Thanks!