Hi thanks for your concern, arthritis is just one of those things that I've learnt to live with, there's ways around it most of the time, Ive just bought an auto Jag for use in town traffic but that's another story...
Looking at your photos, it maybe just because I can only use my phone to view them but I can't actually see if anything is broken. On the throttle plastic there should be a lug that when rotates stops again the throttle screw. If it is broken you can pull the butterfly plate out the carb by unscrewing the plate,then the shaft just pulls up. To be honest though if it is broken I would just buy a copy carb. They seem to work well and at 8quid odd it's a cheap fix.
Just looked again, just to avoid confusion, are you talking about the one nearest the engine or nearest the air filter. If it's the latter then it's the choke lever that's missing, unless you've removed it for the photo.