See my above reply where I've already explained how to sort by an external table. You need to set Oder By to Advanced and add your custom SQL ORDER BY clause there, which needs to be a subquery. You can do the same for filtering, which directly adds to the WHERE statement of the userlist query. There is no functionality to add joins to a userlist query unless you do so by acting on the appropriate userlist triggers and extend it using custom coding. See the below MYSQL documentation regarding order by if unsure how order by sorts in SQL.
dev.mysql.com/doc/refman/5.7/en/sorting-rows.html
dev.mysql.com/doc/refman/5.7/en/order-by-optimization.html
Please in the future do not include your entire post in a confidential tag. Make public what is possible and do not include login credentials (which I have removed) even in confidential tags.