The Lookup element is a powerful way to pull a list of records from Salesforce and allow your fillers to select a record from that list.
But wonders never cease and two users had a great request that challenged us - so we did it. To put it simply, they wanted to add relationship queries to control the data in the lookup - and now this can be done.
Thank you, Daniel and Boaz for taking our Lookup another step forward! 
Enjoy!