We are using both internal/native and external objects. And we need to have a 1 to Many relationship from the Internal to the external object. We know it is not achievable for now, but is this something you are planning to change later on in any future release ?
Are you using external table or remote database?
Please raise an enhancement request. Your feedback is valuable and it will be monitored by our Product Management team. They will review during the planning phase of each new product release.