I’ve got an ongoing issue with my 9 speed ultegra shifter. the lowest gear detent won’t keep the chain on the sprocket. The cable and limit screws are set properly. I have a feeling, that the detent in the lever is damaged in some way. Could I dupe the shifter by moving the limit screw on the smallest sprocket to second smallest, and run the shifter as an eight speed negating the ninth detent? We are headed for Colorado and the big sprocket will be useful.

I’m sure you could achieve that – but maybe by tightening the cable by “1 cog” at either the clamp or using adjusters (if there are any) rather than moving the stops on the mech

That’s worth trying in case the limit screw can’t adjust as far as one complete sprocket.

It will.