Confirm there are not already settings or features that do what the shop is asking for- Confirmed. There are currently no built-in settings or editable options to customize checkout verbiage or automatically trigger a "Log In to Redeem" prompt when a customer enters a gift card while checking out as a guest.

What does the shop want the product to do- The shop wants the checkout system to either automatically prompt guest buyers to log in/create an account when applying a gift card, or allow the shop to customize the checkout verbiage so customers clearly understand why their gift card isn't working without an active account.

Why/how would it improve sales or efficiency- Shops frequently need to issue gift card credits for refunds to customers who don't have pre-existing accounts. Clear login prompts ensure these users can effortlessly redeem their refund credit without support intervention.