I think you can subscribe to individual magazines on kbin, then just show your subscribed magazines. This means you still have to subscribe to multiple communities. Eventually, it should settle with better modded ones reaching critical mass after some time. Everything is in flux right now, what you’re looking for is better done when communities are stable.
The only thing that’s a bit painful now is finding narrow topics. Reddit had grown so big, you can almost guarantee to look for niche topics. On here, you’re better asking /m/random.
In a year or so, if fediverse can grow nicely, maybe we’ll be asking top level instance to recommend the best community, and rebuild your niche collection.