You can open up a .dsf in a text editor. Notepad ++ works better than regular notepad for this—it can read all the code and give it a clean nested look. The format looks like .json and it's not too hard to figure out the structure.

This means you can make a symetric morph of, say, a smile wrinkle, make two copies of it, and delete the negative vertices in one and the positive in the other so you have one for each side too.

Now I need an easy way to calculate bone push values to go with some of the more radical morphs. : )

P.S. Don't forget to halve the "count" value when modifying the .dsf. (Not the "vertex_count"!)