Solved, but leaving here for others..
My understanding of DB's is 'imperfect' shall we say. Information.schema can be accessed from any connection. I created a new custom sql in an existing connection and a fake column to join with my other tables:
SELECT 1 as User_ID, max(create_time) as Update_Datetime FROM information_schema.tables
Works fine (as long as you have a User_ID of 1 in your joining table)