On my CK 30 there is a little knurled knob in the location the OP showed that is attached to a piece that goes across to the 3 point hitch arm lift /lower lever and can be moved up and down and tightened to stop where the 3 point hitch lever stops. I believed it was the draft control, is it not? If not then what is it? Are you not allowed to use it for anything else but plowing? I don't want to break any tractor draft laws but I don't do any plowing and would hate to have a good feature go to waste.