Sadly, the game's entire UI is fixed and can't be scaled.
If I try to implement this someday, it's going to be a really huge work. I can't make any promises.
Understandable.
I did think that it would have been done in a fixed way as it seems to be the way most people do it. Knowing Unity as little as I know from just messing around with VRC Avatars, the little I've seen, it seems that UI scaling has to be thought about before starting to make the UI.
Hope you can manage it someday, if not, I guess it just is what is. xD