There is only one 'Retail Product Hierarchy' in AX but there can be multiple 'Supplemental Navigation Hierarchy' records you can configure. These supplemental hierarchies can be attached to your store POS.
If you wish to do this, you can do it through the 'Channel categories and product attributes' form. The user should select their appropriate channel and change the 'Category hierarchy' field to the hierarchy of their choice.
Some times you will make this change and switch over to the POS and not see the hierarchy immediately. You will need to make sure to run the appropriate distribution job to push the data to the store, then make sure the store refreshes this hierarchy. If its not done refreshing, it may show up blank initially. Waiting will usually resolve this issue. I am not aware of a way to speed this process up at the moment.
Figure 1 - The Modern POS navigation setup
Figure 2 - The setup for the POS hierarchy