Right now, the switch in my brake lever is connected to the purple wire as described. When I trip that switch, it turns on the regen to the constant level set in the software.
Are you saying that if I plug in the second throttle, the controller should automatically detect its presence? So that then when I trip the regen using my brake lever it will turn on only a minimal amount and then allow me to turn it up using that second throttle to the maximum level set in the software? Because that's what it sounds like you're saying, and that's what I'm expecting, but it was definitely not happening when I tried it.
I suppose it's possible I did something stupid like not having the throttle wires connected in the right order, but I was pretty careful.
This is on a Sabvoton controller from LA Ebike as advertised here by you.
Did you get regenerative braking working?
Right throttle is go.
Left throttle is variable regenerative braking.
please post your results.