This system wide Refunds Default setting in weintegrate controls which payment method is loaded into ‘Payment method’ field on the Refund Receipt in QBO.
The dropdown list of available options in weintegrate is based on a combination of available payment methods from your QBO account.
It is your responsibility to ensure the payment methods you set in Shopify match with the payment methods you manage in QBO.
The Refunds Default screen is available in both the Configuration Setup Wizard and the Connection management section of the app.
Click here to learn about setting the Who assigns the transaction number default for integrating with QuickBooks Online.