enrol/otherusers
From MoodleDocs
This allows you to associate users to a course without enrolling them. This means they have a role but and can carry out tasks relevant to their permissions but will not appear in the Participants list. An example of this would be assigning a user to a Principal, Manager or Helpdesk type role to provide them access without confusing the participants list.
Note that this page will also provide a list of users who have been assigned a similar role at Site or Category level.
Assign Other Link
Assign Other Users screen
