To subdivide products in Shopping campaigns using your own set product structure, you should use:
- AdWords labels
- Starred items
- Multiple data feeds
- Custom labels
You can run your Shopping campaign using just the “All products” product group, or subdivide it into as many product groups as you want using product attributes like category, product type, brand, condition, item ID, and custom labels.
Read more here: https://support.google.com/adwords/answer/3517331?hl=en