Cannot rename account name

I added an arma@k2r67kry5haud25b.onion account, so I could use the Tor jabber server.

But Tor Messenger keeps telling me that my password is wrong.

Matt thinks I should have written arma@tp.o, and then set the onion server in the "advanced options" menu.

Maybe this is true, or maybe it isn't, but I wanted to change the account name and there is no straightforward way to do that. Do I really need to delete this one and make a new one, and transition the password/etc over?