Manage dashboard users with SSO and Local users enabled.

Hi,
I would like to understand if any of you share this scenario and if yes how do you handle it.
In a mix authentication, where you can signin to Qualtrics brand using either sso and local login, when I am managing users in the dashboards, often I need to import users using a .csv. when doing so, when I jmport a user email from a user which has not yet login to qualtrics, this will create a new user. Resulting in me having to check always if the users that i am importing have previouly login to Qualtrics.
I suppose that one of the ways to do this is ask upfront for a list of user which will login uaing SSO, this was I can match their future username format when importing.
The challange with this is that our directory is very large and its a result of aggregation of multiple domains that resulted of aquisitions during years. Meaning that finding out the users id is close to impossible.
While i understand that most of the challange is in the complexity of our directory, i wonder if anyone has come across similar scenario?

Thanks