I’m thinking of Alexandrite as the chocolate shell over my lemmy.world ice cream cone. Alexandrite is not an instance, correct?

Correct

I have not found a place on Alexandrite where my subscriptions (joined communities) are listed. Is this not yet available?

Top-left hamburger icon

I assume that if I join a community in one (either Alexandrite or Lemmy.world) it will sync with the other. True?

They’d be exactly the same - you can view lemmy.world via https://a.lemmy.world which maybe makes the relationship between the two more apparent.

I’ve joined communities in Alexandrite, but they don’t show in the list of subscribed communities in lemmy.world. That just may take more time. Yes?

There shouldn’t be ‘sync’ issues, they should have the same content. It’s complicated by how boned lemmy.world is though (it barely ever loads for me, and its API responses are currently out of whack)

Hope this helps. I really like using Alexandrite too!