Well, if you tried clicking on a category in the menu, you would notice that there are additional search parameters that look like this:
The ProductCategoryID would change based on which category you clicked.
Well, you can make modifications to the menu using Menu Writer, you would have to add some additional code to make it work as it should though, that is why its not recommended.
I apologize if it seems that I was trying to give the least information possible. It was not my intention to make the instructions unclear. It is just emulating the behavior of the previous menu, so the url parameters can be found by clicking on the product category in the menu to get the results.