Does this also work for existing accounts within 1Password with e-mail addresses attached? I can't find anything in the 1Password interface to change a login f

Does this also work for existing accounts within 1Password with e-mail addresses attached? I can't find anything in the 1Password interface to change a login for current accounts. All the language makes it sound like it's only upon login/account creation. I guess the fallback is just manually creating one in Fastmail, but it's a bummer if you can't just do it from one place in 1Password.