Bobert - Best odds for doing what you want is to disconnect the seat switch and just leave the wires - either one, or both, of them - hanging (taped or tied down, of course, so they don't flop around).

There are detail differences in the specific models that might make that disable something else, but odds are good that the one disconnect should work.

The engine kill function is caused by CLOSING a switch, and the open wire simulates an open switch - which is what you want. If you unhook a kill switch wire, DON'T connect it back anywhere else - at least until you confirm that the open circuit does something else you don't want.

The backup override button mentioned on the Deere could be a pushbutton OFF-MOM switch (NC, OFF-MOM), that disconnects when you push the button, but it would need to be in series with the safety switch that closes when the shift lever goes to Reverse - preferable with nothing else between the two. You could also put a normal On-Off switch in the same place, and ON would let the interlock work normally but OFF would prevent it from killing the engine.

Usually, the Reverse sensing switch is just under the plate where the Fwd/N/Rev stick comes out, and it's just a leaf spring that the shift stick hits when you go into the R slot. The plate itself likely comes off if you pull 4 or 6 sheetmetal screws - or on the high dollar models ordinary screws that go into nutplates. You usually have to unscrew the shift lever knob to get the plate clear off, but all you need to do is lift it enough to see the switch.

John