by Sakshi Goel.
Hello George
You have missed one permission "Manage advanced grading template form" to the role you have created. you have only given permission to share it. Just allow the capability for teachers "moodle/grade:managesharedforms" to grants the ability to edit and remove any shared template, even those originally shared by other users. from Settings > Site administration > users > permissions > define roles > Teacher. Then teacher get a option on the advanced grading page under course administration to delete the form.