Welcome to many to many relationships and a join table. I'd put a portal to Object in Locations--your join table for linking objects to the current locations record. Objects in locations::objectid would be formatted with a value list for selecting an existing object.
Then use a button with a script to create a new record in Objects plus a new record in the join table that links the new record to the current location. once that script is run, you can enter data into any fields from Objects in the portal row of the record linking to that new Objects record.