Custom user attributes are in table UNIFIER_EX_USER_INFO;
I don't know any table but, "Company Workspace" -> "Administration mode" -> "Data Structure Setup" -> "ER Views" gives Information about the tables.
I think you can see all unifier tables anme inside unifier user name with you had done configuration.
(User which you had added manually and granted access).
You will see that inside "Other users' at bottom of list in database.
I always wondered about this: can self-hosted users see the entirety of Unifier’s schemas? The question of table names seems to constantly arise (I must say, BIP would be somewhat less of a chore with a relational diagram).