You should be able to enter a value in warehouses::id_owner without enabling "Allow creation in related table". Just enter the value. Is this not working for some reason? Or do you have a problem determining what value to enter?
You didn't actually have the ID field on your layout. In order to enter a field, it has to be present on the layout:
I've attached a modified version of your file with the necessary changes. Hope it helps.
i´ve tried to do as you but using the owner_name (text) as relational field between Warehouses and Owners tables. It didnt work (i think because filemaker creates a many to many relationships). So i will go for your solution since it works nicely