Choose 'Site administration' -> 'Courses' -> 'Add/edit courses' Select the 'Edit this category' link for any of the listed categories (e.g. Miscellaneous) A Category ID number field is now available, complete with appropriate tooltip help. The field now also exists in the database in the course_categories table. Try both adding one idnumber and later modifying it. The idnumber is properly stored and viewed on re-edition. Edit another category and try to insert one already used idnumber, message about id number already taken should be shown and prevent the offending idenumber to be saved. Edit another category already having one valid idnumber and try to modify it to one already used idnumber, message about id - number already taken should be shown and prevent the offending idenumber to be saved.