im pretty sure the entire opening to the fellowship of the ring was extended but not in a way that you could branch. for those who have seen the two you know what im talking about.
the theatrical starts with frodo reading against a tree... as time goes on we finally meet bilbo who's writing his book and describing hobbits..
the EE starts with bilbo writing his book and describing hobbits and then after that is all done frodo is reading against a tree...
again for those who have seen the two, you know exactly what i mean.
i just would find that hard to do by branching.