Hello RoyoX
Both these tables are standard tables and partner functions being created are driven by what partner function schema have been configured for particular vendor and customer account groups.
If you are looking at corresponding customer for a Return vendor then the customer partner function schema should be modified which should take care of these entries for you unless you want to populate or default something specific for any given purchase org or sales org which then can be a customized ABAP code.
hope this helps.
thanks & regards
Rahul