I cannot see a cable or lever anywhere
To remove the dash top you would have to tilt the whole dash assy to the rear. Tilting it back is all you have to do. The FSM has instructions.
The cable must hook up behind the knob somewhere doesn't it ?
Take a look at the picture tomblue01 provided. Those tubes go to the heater core. For the umpteenth time, to see the cable connection you have to tilt the dash to the rear.