Returns are not managed in our connectors. The reason is simple. Every return is exceptional case:
some customers get money back
some get credits of store
some should send product back (and return label should be sent)
some should throw away product
some just keep product as gift
for some replacement should be sent
All is unique so handling of returns is kept as a manual process. And customer support defines what to do on case-by-case basis (manually doing needed changes both on e-Commerce and Odoo side)