I've poked around the controller, and managed to find pads for cruise control, speed limit and reverse on new design board.
As you can see in the pic, L is for reverse, Q is for cruise control, X is for regen and pad just above XS is for speed limit/low power mode. When I activate regen at maximum unloaded rpm, voltage does seem to jump, but this will need to be checked on a strech of downhill road.
Speaking of regen, what I noticed is when rpm decrease to almost a dead stop, wheel locks up completely, and you can barely move it by hand, so it seems that controller is actively locking the weel, ie. using power, so I'm not sure how much this feature will be useful, but it seems that regen can be used to bring a bike to a dead stop. Will test out this later.