Wow, I find it hard to believe that this was not reported until now. I just upgraded to Fusion 16 and not having this hotkey feels like someone just cut off one of my fingers. Being able to nudge selected key frames 1 frame at a time and with the shift key 10 frames is very useful and a super quick way to make adjustments.
I really hope you will provide us a hotkey somewhere that will give us this feature back soon.
Thanks!