Shopicraft Bought Together

Show "Frequently bought together" under the buy button: the product and one to three complements, a box each, the total and one button that adds them all. Pick the pairs yourself, or let Shopify's own recommendations fill them. Add a discount for the whole set: the page shows the discounted total and the checkout charges exactly that. A second block suggests products on the cart page. Sold-out products are never shown, and each complement has its own option picker.