Choke's do not have a lock on it as far as I'm aware, it is a Throttle / Idling Control Knob, but the use for it you are correct.
Uses
Cold Engine
Winch
Tonys "Lets you hold the engine revs up without using the accelerator, good for rough driving where your foot would be bouncing on the pedal" is not listed in the owners maunual" Says something big black letter, Avoid driving the vehicle with the throttle/idling control pulled out.......
But I agree with Tony, and have used it plenty of times before.