Is your feature request related to a problem? Please describe.
I think a fairly common use case is updating the subtitle position offset. If you're using multiple streaming sites or playing a video with embedded subtitles, you end up adjusting the position offset fairly frequently. It would be nice if you could do that with keyboard shortcuts as well.

Describe the solution you'd like
Add keyboard shortcuts to increase or decrease the bottom (or top) subtitle position offsets by a set amount.

Describe alternatives you've considered
Alternative is updating them in settings

Additional context
I actually already implemented this in my local asbplayer repo. If other people find this useful, I think it could a be a "nice to have" feature.