Lemmy’s API doesn’t have a direct way to do that, unfortunately.

Tesseract (web-based lemmy app) used to have that before I took it out. After the ranking metrics were removed from the API, it was hard to sort them other than by new/old or by score. When you have a mix of active and inactive communities, it didn’t work great without the ranking metrics being there.

You can still group communities, but only for organizing them or (in the dev branch/next version) applying filter policies to communities in that group.

I may revisit the idea if I can figure out a better way to generate the custom feeds.