I see that says 'has to be local only, not federated' (same issue also discussed on github).
'Local only' suggests to me front-end, i.e. info stored by browser. In that case people who are often switching devices would have to re-organise on each one, which could be tedious.
So isn't there something in between local and federated - i.e. saved by the instance as user-settings, but not pushed to other instances?
Maybe there could be some manual copying mechanism, so a user who organises a big set of communities could share with others.
(This reminds me of mastodon 'lists' and various ways of organising and transferring them).