I believe it should be one of the front levers. One of the front ones change distance (front to back) and the other lever changes the angle of the seat. It feels like the front of the seat it self moves up and downHi, me again.
I read somewhere that the seat base is adjustable for height and angle. I can't seem to be able to adjust the angle /tilt on mine. Height is fine, the button on the side is multi use. Is there a knack to it?