We have created a product tree with product categories. In the standard reporting, you can't automatically group the product categories on their parent (ex. group "bike/wheels" and "bike/frame" together under the parentgroup "bike")

I think this parent group is the field parent_ID in categ_ID in the model product.category. But how can I actually get this parent_ID field to show up as a field to select/filter/group ? I'm 100% not a programmer, so please explain in plain english ;-) . Thanks in advance for any help!