What I'm trying to do is two key concepts (that are trivial in DB) consider there are two tables A and B, where table B has a relationship to table A (entity relationship in power apps)
Now Scenario 1 - add New entries in Table and make sure the proper key relationship is maintained back to table A. So say you have a Person and you want to add a new skill for that person. So I go about creating a new form for adding skills, pass it the person ID and they try to get the form to auto fill in the linking person ID. Power app doesn't like that one bit. I have a formula to fill in this value BUT since it's defined as a lookup the system save the value in the backend db when the form is submitted.
Second I want on a single form to show a person summary AND the skills they have. So when you choose different people this should retrive all the skills they have. So I go about creating one collection to show a single persons information, (via filter on Dropdownlist), then use a second filter with the "in" condition to find all records in table B that have primary key IN Table A PersonID...
I managed to make some progress but only by deploying a work around that was to basically ignore the entity relationship by creating a new column that is an integer, and then use a formula to populate the column (in Table B) with the Primary ID integer from Table A.
This must be a WTF on my end becuase it completely defeats the purpose of having relationships that help referential integrity