Completely hiding a course from everyone but a particular group

[danhz (Dan)]

I wanted to follow up here and mention that I have also tried this, to no avail:

How to hide courses from "Discover New"?

I’m running Koa, and I have 10 courses. 8/10 are more like labs, so they’re not supposed to be listed for students. I have their advanced properties visibility set to “about”, so that we can link to their page and let students register to see their material when needed. So then they properly don’t show up in the main site. However, when someone clicks on “Discover New”, then all the courses, including our various sandbox testing courses show up for the students. How can I hide courses from the …