As I am sure you are aware, many accounts allow a user to sign-in using different kinds of credentials in conjunction with the account password, e.g., a username, a phone number, an email. We do have the functionality to add "Custom Fields" in Locker, however we do not have an option to select multiple fields as valid 'usernames' to be used as alternatives when signing into a single account. This would be helpful.
The only alternative is saving those credentials in custom fields (without the autofill or other functionalities) OR saving the same PW multiple times with different values input as "username" for each.