You can now issue a specified amount as new store credit when processing refunds. This can be done in addition to refunding amounts to the original payment methods. If a customer requests a refund to their original payment method after already receiving a refund to new store credit, you can accomplish this by specifying a parameter that allows over-refunding. Note that this parameter is disabled by default.
This is a companion discussion topic for the original entry at https://shopify.dev/changelog/refund-to-store-credit