Hi Han,We use the org field to define categories since all the courses in our platform will be held/run by ourselves.
If you don't want the people to see a new course the easiest way is to set the anouncement date to somwhere in the future (2030 or so)We have defined a special category in our theme to create hidden/private courses, aswell we have a "test" server where teachers can use to manage>generate their courses.