Sorry to hear you've had such a bad injury, I had a serious injury to my right arm last year from which I am still recovering (elbow injuries are tough). I'm right handed, I found I could use Mathematica reasonably well with my left hand using "Sticky Keys" (a Windows features, so I didn't have to hold two keys down simultaneously) and that the function name suggestion features helps a lot, often only the first three or four characters were needed. Of course typing longer comments and the like was slow doing it one handed, I could see speech to text being helpful for this.

I am very sorry to hear about your injury, Kathryn! I hope it gets better soon. I think this is really interesting accessibility question. Perhaps @Kyle Keane knows something, -- he has been very helpful some relevant conversations. I think this question is also closely related to "How to comprehensibly read Wolfram Language code out loud?" Maybe if some data are accumulated in answering one of these -- the other can use those data too. I generally have seen some sources around these things being done in other languages -- so I do not see any reason for not implementing it in the Wolfram Language:

• Speaking in code: how to program by voice (from NATURE)
• Tavis Rudd talk
• Coding by Voice with Voice Attack: a Practical Guide for Programmers
• Code with voice
• https://www.voicecode.io
• Generally a web-search (like voice OR speech to code) returns a lot of good results