We are looking to sell a product with 8 different color variants and I'd like to upsell them on additional colors of the variant as separate product but sync the inventory.
For example, say we have a necklace where the customer can choose the charm they want on the necklace. We have about 100 of each charm available. Then after they add to cart, we upsell them on just an additional charm. The charms can also be bought individually.
How can we sync the inventory between the individual product charm and the same charm used as a variant in another product?
I recommend checking PickyStory's In-cart upsell deal.
In-cart upsell enables you to recommend related products on the cart page to your customers. It allows you to control which bundles will be promoted in the cart and it's also Auto-synced in your inventory on individual product basis.
Feel free to reach out to us if you have any questions.
Try out this amazing upsell app to offer product variant as upsell in your cart, here is the app link: https://apps.shopify.com/icart
Hope that this app will help you to fulfill your requirement.