That lever is in the same place as the step up and step down unit.
This lever was to discinect the rear wheels so you could let the clutch out and the power lift would then raise the cultivator.
Farmers--including my neighbor used to cultivate up to the fence to close then the only way to raise the cultivator with the power lift was to jack up one wheel so it would spin, thus raising the cultivator.
This unit simply did the disconecting to the rear wheels. They made a aftermarket step down, or it could have been from AC. My one neighbor had one that was a step up, a nuterel, and a step down. I have never seen another one in the last fifty years, and I have looked hard. Many old timers told me there was no such a thing, but I drove this one many hrs as a child.