Yep, we already have it but when you have 2-3 level categories like us, only the lowest level category shows actual product count on the Catalog > Categories screen
All upper level Cats just displaying zero's. It seems to do simple count from products_to_categories. But zeroes have no informational use. We think any level category should have an
aggregate count of all the products
beneath, no matter how many levels. Is it possible to enhance the formula? Real numbers would help better manage the stock.