i’m saying that if indexed is screwey… then swap to friction where you can have a bit more control in precision about where one would want to “leave” the shifter so as to keep it from skipping about. I’ve had to do this when borrowing sram cassettes as well as when mixing 78 and 7900 with 7800 shifters. Hell one time i ended up with a 9spd on the back (flatted in the garage and just grabbed a wheel) and friction sorta saved the ride.