While I am on board with the idea, I don’t think it should be a programmatic solution at the community level. Rather, either the third party app or the server (let’s say Beehaw for an example) should allow for the option to create collections based on community identifiers. It would be more of a display function.

The reason I think this needs to be done at the user level is because everyone has their own organization models. At one point, I had all my subreddits aggregated by Library of Congress Categories (since may home library is organized that way). Some people may want to put c/Beatles in a Music category, while others may want Bands or even others by genre.

What would be nice is if the communities had tags to identify their subject matter. For instance, c/Beatles could be #britishinvasion #music #beatles #band #60srock etc. That way people could look by tag and aggregate that way (plus it would make it easier to find c/GeorgeHarrison c/PaulMcCartney c/JohnLennon c/RingoStarr ;-) )

The way I would see this play out is that the user would have to option to create a “Super Community” and give it a name. Then there would be a search by name, tag, subject etc. and the results would have a toggle that would add, or subscribe and add, that community to the super community.

A solution like this would preserve the sovereignty and integrity of each of the servers. All the servers are offering are possible some more discrete identifiers (should they choose) to make themselves more findable. The control is placed on the user to organize and curate their selections.

I don’t mind responding to different communities with similar subjects. I did it all the time on Reddit. But it would be nice to, say, focus on my “Apple” super community or my “Worldbuilding” super community. When you have eclectic interests that span a vast array of topics, being able to aggregate “like topics” is a boon.