You can add any number product variants/attributes and these will be tracked automatically on purchase/sale. There print barcode/label page for each product will show the new barcode image if there are variants available for the product. This will help you to manage the products well specially for those who need to track the products attribute
i.e, sizes and color etc.
Variants are single level and if your product has nested variants, then you can add the as Red Size 5, Yellow size 6 etc. You need to add these only once for each product.