Waiting lists are not only available for single classes but also for the whole course.
In order to add one or more people to the waiting list of a course you will need to make sure that the waiting list is enabled for that activity (Settings -> Activity)
Once you have defined the criteria for your research, the system will provide the results in a table on the right.
Click on the required course and click on the button to add people to the waiting list for that course:
Type in the name/s of the people you intend to add to the waiting list and click on add.
It will be also visible in the person's profile: