Hihi o/

Could you describe a little about how you'd want the interface to work?

Couldn't seem to reply to the email, but.

I think having something like NewPipe with a horizontal list of subscription groups being put on the top is already good enough, but I was thinking about it being put on the side for larger screens like on desktop. The default view could show all new videos from grouped and ungrouped subscriptions, or perhaps just a list of all the subscriptions you have currently.

Ok, so you want a way to create groups, and put subscriptions into them, and then for each group, you want to view the channels that are in it, and the recent videos from just those channels.

This is going to be pretty low-priority due to the amount of work it will take. In the meantime, FreeTube has this feature, if you are interested in using that.