You can view the grades of concluded student enrollments, but you cannot change the grades.

You can delete an enrollment in your course within your course Settings in Canvas.

Note: If students are added via SIS Import, instructors will not be able to remove students from the course, regardless of their permissions.

If you use terms, you shouldn't have to conclude any enrollments because it is automatic. However, if for some reason you want to manually conclude an enrollment, follow these steps.