Nested Categories

The inclusion of categories for time tracking is great except for when I have lots and lots of categories to add. For example, I would have a category for Projects that would then include all of the projects (maybe 100 entries). It would be nice to have some structure and ability to track these in a nested format where it was Projects/Project Name.

Is there a way to do this without having such a flat structure and extensive manual input and formatting?

I generate quarterly reports on how time is being spent in our department so being able to better organize this would be extremely helpful.