Username alias?

Is it possible to create a login alias for a user in XP?

You can login with anything you like, as long as you create your own idprovider.

I got user accounts based on member numbers from an external ldap server, e.g. 11223344. Now the member numbers are changing, and I have to support login using both new and old member numbers for a period. I don’t want multiple accounts in XP for the same user because of users’ access to data in XP.

As far as I can see allowed login attributes are email and login. Does any of these support multiple values, or are there other attributes that will allow login?

So, you are using the Ldap idprovider?
Thing is that XP only needs to store a unique identifier that does not change. If it changes, it is a different user.

How the idprovider authenticates is not relevant for fields in XP. Anyway, you can persist as many fields as you like in XP with profile scopes.