Right now if you're editing a type of anything (railings, section views, etc) that uses other nested families, you need to exit the type editor, reach out for the family and then edit the family.
Imagine how great would be if you could edit the families that build a type of something just by clicking at it, as you can edit a wall layer material by clicking at it. Ex: when you're editing a baluster placing rule in a railing, with a click you open the baluster familie and edit that one particular detail that will make it all look great.
Regards