How to Modify Look and Feel Extensively?

[tucsontier@yahoo.com]

I've also just started looking at this. This is my only application left that I can't adjust. I can do a bit in Look and Feel, but then symbol properties have to be used for the rest, and, even then, I can only get 80% there. Modifying symbol properties is not a great option, because I share the model with others.

Is there a way to modify the underlying XML, CSS, or other (theme) code?
Can one add themes externally?