When a category expand/contract icon is clicked, the grader report must be re-drawn so that the selected category either becomes 1 aggregated column (if contracting) 1 row below the previous position, or a header over a number of sub-objects (if expanding) 1 row above the previous position. Colspans and fillers must be updated, as well as user preferences ('grade_category_' . $categoryid, GRADE_CATEGORY_EXPANDED) (or GRADE_CATEGORY_CONTRACTED).