I have a PowerApp which saves data to a Sharepoint list called Beds In. Within the PowerApp there is a second part to it whereby I need to save a name to each of the records in the Sharepoint list where the unique reference field matches.
I have tried this to look for each of the REF fields that match but it only updates the first instance it finds and not all instances.
You are going to need to use ForAll in conjunction to loop through all the records. Check out this video I did on Repeating Tables. I do very similiar to what you want to do, just in a different context. My save button loops through all of the records and creates them, you would just need to look through and edit.