Each group can be a father- but also a child-group
Here's how you create such a relation
1. Go to the Products tab and click on "Products".
2. Click in the overview on the same name as the product group.
3. In the Edit Product Group Screen you will see on the right "Child groups" with an overview of the
various Child groups below.
4. To create a Child group, click on the green "Add" button.
5. In the next screen, enter the description of the group and click on "Save" so that the new child
group appears in the overview.
6. You can create an extra group under the correct Child group.
7. You can fill the Child group with products by first clicking the right group.
8. The group opens and behind "Products" you need to click on the green "Add" button to add