The Head Teacher (the "Head Teacher" in the interface) is an expanded role in the course: they manage the educational process almost like an administrator, but without some of the administrative and financial actions.
They edit courses and lessons (if not restricted), manage students, homework, and the schedule, moderate comments, configure the rights of regular teachers and students, assign mentors, and change the role from "teacher to main." The customer list, student passwords, paused learning from the menu bar, and salary tiles on the teachers' tab remain the administrator's domain.
To assign a primary instructor, open the Courses section, select a course, go to the Instructors tab, and select the role from the list.