Difficult to trace Inee!

It looks like there is a ring of black ground wires around most of the button switches , and each switch then has a signal wire at 10.6 volts dc.
I also presume that the motion is operated when each of those signal wires is grounded by pressing the button. All the wires seem to be supplied by the 34 wire ribbon connector which also connects to both Microprocessor (Bottom) board and to the feed regulator / potentiometer board on the back of the feed rate switch.

Difficult to follow the ribbon connections.