I know this is old but in case anyone comes across this like I did…
I found the answer on David Lindgren’s Medium post “How to move keyframes with the keyboard“. The name for the command in keyboard shortcuts is “move keyframe 1/10 frame(s) earlier/later”.
https://davidlindgren89.medium.com/how-to-move-keyframes-with-the-keyboard-80466e35914e