When editing an order, Edit Order automatically refunds an order after the initial edit if a refund is due. But if you want to add another refund a few hours or days later, that's when you'll need to go back to the original order to do so.
Due to a limitation in Shopify, refunds are not able to be posted when issued through an edited order. We are in the process of building a feature to remove this limitation.
How to perform a refund on an edited order: