clarification:
that's not my bike there
My bike is a road bike with a Retroshift for the RD and a stem shift for the FD (both levers are SL-1050s)
I wanted to mount my FD lever onto a thumb shifter, but didn't want to pay the big premium for the Paul's Thumbies.
I saw this old XT thumb shifter today and wondered if that used a boss like a downtube shifter, because I could get one of those super cheap and mount my SL-1050 to it
I've learned that's not the case.

Now I'm debating a Paul's Thumbie or a barcon for the FD. I'm leaning Barcon if I can find a single one for cheap.