A few hints for organizing your custom race courses in VSK4.
Instead of dumping all your courses into one folder (the MyChallenges folder by default) you can organize your courses into any directory structure you like inside the GameData\Tracks\Challenges folder (I will call this the Challenges folder from now on). For example I have the following folders inside my Challenges folder (besides MyChallenges and Downloaded):
ITBYC - for the "official" itbyc team racing courses.
TeamRacing - Other team race courses I have
OffShore - Courses for the Offshore cruiser
Testing - Courses currently under development.
When you are in the Course Editor and save a file you can navigate around the directory structure rooted at you Challenges folder and save the course file wherever you like, you don't have to always save it to the MyChallenges folder. Similarly, when you host a race you can navigate around the directory structure and select courses from any directory under the Challenges folder without having to sift through pages of irrelevant (for the moment) courses.
I think this is one of the "unsung heroes" of features in VSK4!