- In the WooCommerce admin backend open the edit product page
- Scroll down to the section 'Product data' and open there the 'Attributes' tab
- From the toolbar at the bottom you can choose to either add an attribute group or an attribute group set. After you selected an item click 'Add' -> All the assigned attributes will get added
Current limitation - Re-adding attribute groups on the product edit page.
Adding an attribute group with an already deleted attribute (without saving in between) doesn’t re-add it at the moment. Simply reload the product edit page, re-add the desired attributes or groups again and you’re good to go.