Check out the shifter/ clutch linkage on Stan Dishongs' Indian, it appears that you could clutch and shift with a simple prod of the rear pedal. This would make a lot of sense on an otherwise hand shift bike. no doubt it was better to keep both hands on the bars. I have had this bike on here before but not a close up.
I used to eyeball this machine on a regular basis when I was a young man. I used to go into Stan's shop in Vallejo a lot in the mid-seventies. He was quite an innovator and had done a lot of interesting things in his life.