Admin can add defect priority but user can add defect priority if admin provide the setting access privilege to that user.
Steps to add defect priority :-
1.Click on "Setting" icon.
2.Select setting from setting drop-down.
3.Page redirect to "Defect setting" and Click on "Defect priority setting".
4.Now click on "create defect priority" button.
5."Create Defect priority" popup window will open then fill details and click on "Save" button.