Dear gregL-5,
You are correct. Currently this can be achieved by creating an intermediary post type to handle the relationship.
To have a direct edit box it would require to create it in the frontend (via PHP/HTML) or in admin (probably via http://codex.wordpress.org/Function_Reference/add_meta_box).
Then you save the data via an action: in admin it's from the WP API: http://codex.wordpress.org/Plugin_API/Action_Reference/save_post and on frontend when using CRED it's documented here: http://wp-types.com/documentation/user-guides/cred-api/
Please let me know if you are satisfied with my answer and if I can help you with any other questions you might have.
Regards,
Paweł