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Is there a way to add an item to the cart that the customer can’t remove? We have some products that automatically come with another product. We can’t just eyeball it because the orders are imported into another system and the second product needs to be added with the first.
The read-only add you propose will need a reciprocal remove function. To make it unremovable from the cart would stink from the customer’s viewpoint because if they decide to not buy the combo, the item will have to self-remove when its twin gets removed. Otherwise the customer will have to dump the whole cart and start over.