By default, when you perform the Cancel/Issue Refund action on the details page of an unshipped Shopify order, the whole order is cancelled. However, if the ShopifyEnableQtyBasedOrderCancellation admin setting is enabled, that same action will take you to a page where you can select specific products and quantities. Then, the selected SKUs will be Split into a new order set to Cancelled, while the rest will remain in the Parent order, marked as Partially refunded. This will allow you to still ship part of the order. Contact Sellercloud Support to ensure the setting is enabled for your account.
Improvement
January 25, 2024