So I often find myself pressing c by accident which means I have to redo my joints or if there is no time left, I can only just leave it. So I though it would be a good idea if we had the option to keep the same joints from the previous frame. I don't know what the key could be but possibly somewhere near the other 3 keys so either x or n.

Uhh
CNTRL + Z
It's already a feature