Super-communities?

An idea that just occurred to me. I was looking for communities on machine learning to join, so I searched https://browse.feddit.de/ and found a bunch. They don't have much content but together they have at least 4 or 5 posts each, which adds up to a few posts, so I subscribed to all of them.

However, now I have no way of "grouping" them so that I can view posts of all communities in my feed related to the topic of machine learning.

I was wondering if some concept of "super communities" could be interesting for Lemmy, similar to "multireddits". People could curate their collection of favourite communities around a topic, over multiple instances, and users could easily subscribe and browse the whole bunch of them.