In my continuing scenario of 2 post-2-post types, 'movies, actors', I have been trying to add a meta_box to my movies page that makes a 'callback' to the actors meta_box that is 'attached' to the movies post_type.
Right now the post-to-post provides a UI to select a related post object, but does not provide ability to add a new related post object, (actor) nor does it display the meta_box field types applied to the related post object (actors thumb, description, birthdate, etc). Also, right now I can only select a single object and not an array, (single actor, not choose multiple actors to attach to movie type).
Basically still trying to edit/add an actor post_type and edit/add the metafields for an actor within the movie post_type admin panel.
I know you said that this possibility is coming in the future, but I was curious if you have the time to provide a code example on how to do this callback.
--Until last night I didn't even know what a callback was, so I am learning quickly. It's actually been quite fun. It's just that we're getting into a realm where there is no documentation available online that I can find to do this type of stuff.