In order to get the categories to only display items for a selected category you would need to edit the intermediate.php and alter the code so that will only display the categories you would like.
One example of this would be to modify the intermediate.php file within the CSSMenuWriter folder like this:
line 39:
<?php if ($totalRows_ProductMenu > 0 && ($row_ProductCategories['CategoryID'] == 3) { // Show if recordset not empty ?>
This would allow for category id 3 to have the items listed below, but none of the others. If you wanted to add to this to make category 4 also display the products you would do so like this:
<?php if ($totalRows_ProductMenu > 0 && ($row_ProductCategories['CategoryID'] == 3 || $row_ProductCategories['CategoryID'] == 4) { // Show if recordset not empty ?>