Batch Importer: Support for populating connection fields (join fields)

Would like to be able to populate join fields when using the Importer. An example would be the "Sort Order" field, which lives on the connection between Versions and Playlists. Would be great if I could import Versions for a specific Playlist, and populate the Sort Order field via the import. This would save time sorting them later, which would be especially useful for larger Playlists.