Hi Russ:

You can use eCommerce categories to do this. 

• Go to Website > Configuration > eCommerce Categories.

• Create the required hierarchy of categories and associate these eCommerce categories with your products in the eCommerce tab of the product template.

• Then go to the shop page of your website in developer mode and turn on the "eCommerce Categories" toggle button in the "Customize" menu. (NOTE: You need to be on the Shop page for this toggle button to be visible)

Now you will get the hierarchy of the categories displayed on the left and if you pick the parent category it will display all the products in that eCommerce category and its sub-categories.