The feature to add a username to a password that was stored doesn't seem to be available on 1Password X, and there doesn't seem to be any way to edit the entry in such as a way as to add a login.
I'm finding using 1Password X really really frustrating due to lack of basic feature parity and essential features.
Since I'm on Chrome OS I have no choice.
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Referrer: forum-search:Can't convert password only to login