Beehaw does not allow for user-created communities. One could pitch an idea to the admins, but should not have high hopes.
Beehaw is planing to test (non-federated) software other than Lemmy in a few months from now, because they are growingly dissatisfied with how the software works (esp. from an admin’s point of view). So if you wish to stay part of Lemmy/Kbin/other parts of the Fediverse you may wish to consider not making Beehaw your “home”. I in fact made this account on lemmings.world, because I wanted to have sufficient time ahead of that in order to “test the waters” so to speak. Pre-Beehaw I was on lemmy.ml, but this was in part because there was no federation yet (making everyone flock to the biggest of ~5 instances of Lemmy that existed at the time).
A few notes though: