Creating Categories within Categories?

Hi, I have a client that provides health care education on a number of programs.  Within the programs, there are dozens of courses, which onto themselves ideally should be organized into clusters/tracks or categories. I'm trying to figure out how to design the site so that: 1.  A learner can see the 3-5 distinct programs they run.

1. The different tracks of courses within those programs.

2. The courses within those tracks.

For example, there are are two programs.  One to manage Diabetes. Another on Cardiovascular Disesase.  Within the program on Diabetes, there are courses grouped under Diet Management and others grouped under Medication Compliance.  Within the Diet Management group, there are courses on:  Cooking Practices; Snack Practices; etc And, of course there are units/topics within those courses. If I use the "categories" attribute to define my programs, what attribute can I use to create/cluster/filter on the course tracks? I have thought maybe the only way to do this is to create category stem codes from the beginning, such as: Diabetes_Diet Management Diabetes_Medication Compliance Cardiovascular Disease_Exercise Cardiovascular Disease_Diet Management But I'm wondering if there is some other filtering feature I can use.  I know there is Type, for All, Online, Offline.  Can more than one type be created?  Can these options be customized?  That might be another way to re-work the system and filtering options. Thanks for input!!! Cheers, MHK