System.User as Generalization. Now in the SAML Module in the CustomAfterSigninLogic I created a new object of my new entity AdditionalUserAttributes
AdditionalUserAttributes is not a specialization of User, but extends it. So instead of specialize a user, relate AdditionalUserAttributes 1-1 to User and retrieve AdditionalUserAttributes over association.
In the microflow you have the [currentuser] available and thus you can retrieve it’s related boolean and from there exclusive-split to your desired followup activity.