Can I somehow block for all or only the groups from logging in?
I see that there is an option to disable login but it will also disable the possibility of creating new accounts or maybe I don’t recognize it?
You want to keep current users from logging in, but allow people that you don’t know to create new accounts?
yes, so they can register and not use the forum until it’s ready
I think what I world do, then, is to make all categories available to staff only. Then they can log in, perhaps with just a “coming soon” category. Or you could spend a bunch of money for development of a plugin that you’ll never need again.