You can do this with /api/v3/community/hide, or in the database by setting community.hidden. Unfortunately this is not available from lemmy-ui yet.
From a comment by nutomic: https://lemmy.ml/comment/16090216
Context: https://lemmy.ca/comment/13891923
Not sure if that feature was known to everyone, so sharing this as its own post.
While I see the usefulness of this, I kinda hate the idea of having to rely upon social contacts to discover communities that would be of interest to me - I’m not terribly social, and I don’t keep a collection of online friends. I come out of my hole, look around, get my fix of whatever I need at that moment, then hide away again. Yeah, it’s pathetic, but that’s my life. Please don’t make my world any smaller.
Are you aware of [email protected] ?