The feature of Multi-instructors - provides an option for teachers to assign one more instructor to the course.
To activate this option go to STM LMS > Addons. Find there the Multi-instructors addon and enable it.
The option ‘Add Co-instructor’ will be accessible from the course page for admin and instructors. You can open any existed course or create one and a new option will be available on the course settings page.
Find the ‘Add Co-instructor’ between the Teacher and Category options on the course settings page.
When hovering over the Add co-instructor option you will be able to select instructors from the dropdown add one to the course.