How to Refund Item on Imported Order

Is there a way to partially refund an imported order? I am creating orders in using POST https://api.squarespace.com/{api-version}/commerce/orders and it appears an imported order only has the "Mark Refunded" button for refunding the entire order instead of "Issue Refund" that is available on a non-imported order.

As the order details were imported from a third party system, the original payment was not processed using a Squarespace payment integration (Stripe or PayPal) and so cannot be refunded directly from Squarespace. You'll need to arrange the refund on the other platform.

Refund is probably an incorrect word for it because like you said it was not processed by Squarespace for payment. I'm really trying to remove a line item from the imported Squarespace order. The use case is the supplier has an in Squarespace to fulfill and one of the items is not available so remove the item from the order.