Forecast categories

I have created 16 stages for the many steps in our sales processes and have associated them with probabilities using the Potential Module probability mapping feature, however, my boss would like to set the stages as sub categories under 6 main Categories

I was thinking I could use the Forecast Category or Type in the Probability Mapping feature, but couldn't see if i could run reports or list views of opportunities using the Forecast Category or Type.

How do you run reports using Forecast Categories?

Also, can I modify or create additional Forecast Types or Categories?