On my installation (Cloudron, thanks @bram ) I closed the free registration of new users to keep control.
In my projects, I can issue invitations but guests can’t register if I don’t leave the registrations open. This should be possible, or you should disable the possibility to invite, which would be a pity.
I love the simplicity of Baserow and the features but I don’t understand this issue.
Currently when you disable signups, no one can create an account, not even when you’re invited. If I understand correctly is that you want to ability to disable registrations for visitors, but if someone is invited he should still be able to create an account?
In the meantime you could temporarily allow the signups when someone wants to create a new account.