This feature is reserved for HR and HR Groups.
Go to a campaign's details page, to the category Performance > Campaign.
Once on this page, click on the title of the campaign you want to view.
Then click on the three dots at the end of a row in an employee's questionnaire to edit the participants.
Then select an evaluator or an extra-signer by typing the first letters of the person's name. The grader cannot be deleted but can be replaced.