He did create a whole scenario for the clone wars, but wasn't allowed to describe it in any great detail. Keeping it mysterious works for the purposes of the story, though, and is justified by references to many historical records having been lost, either to the rampant destruction or in an attempt by the Empire to rewrite history to reflect their own perspective.

But yeah, I really would like to know exactly what it was that he came up with. Interestingly, his first outlines had the character that would become Joruus C'baoth originally being an insane clone of Obi-wan! That could have been a really weird and twisted story thread, but he wasn't allowed to do that either, and of course it works very well in its final form.