My personal opinion is that I don't care about the secondary authors.
Which is why my solution simply pretends the secondary authors don't exist.
You wouldn't be able to search on them.
For anthologies this can become awkward, naturally.
Still, I can't really think of a better solution.
EDIT: If you really wanted to, you could make the secondary authors go in a subfolder of the main author. Personally, I don't like that idea -- it seems like it would just make things
too complicated...