Unfortunately, this is a manual process student by student.
Always add the competencies to the learning plans and the competencies to the courses before the student start the course.
I now use the plugin - Monitoring of Learning Plans. https://moodle.org/plugins/report_lpmonitointring
If all students within a learning plan should have the competency that plugin has the feature to rate all students with the same Rating value.
Unfortunately, it does not give you a list of student to choose from, if all students have not yet completed the course.
Kind Regards