We use the variants system of to bundle and upsell products.
The app allows to create bundles for the product selected this will help the merchants upsell the products. Also since its based out of variants they can create bundles with respect to variants.
Link Separate Products with Size, Color, and More.
かんたんに商品のオプションを追加できる日本製アプリです。5種類のオプション形式を用意しているほか、追加料金の指定も可能です。...
Variant Options Info, Color Swatch Name & SKU in Product...
Variants on collection page & Collection filter by variants...