I really don't know how to be clear with that, so I'll try describing the details.
I'll always have categories with undefined number of subcategories:
The first category is my main menu, but the cat-B is not subordinated to the cat-A. Actually, I wanna to them work together.
The pages will always displays posts from both categories
(eg. sub-A1 AND sub-B3; sub-A(all) and sub-B(all) for default).
But I don't want to do it by naming a specific category in query_posts.
There is a smart way to do this?
(a better example)
all | flowers | cars | toys
all | red | blue | green
By default it will show all objects/things and colors. If I select flowers and red, that will show only posts with both categories.