As of now, it seems like there’s no direct way to add gift cards via the cart API from the POS UI Extensions. Shopify’s documentation doesn’t currently support this feature, but future updates might address it. A workaround could be to handle gift cards through Shopify’s admin or POS interface manually, or potentially use a third-party integration. Keep an eye on Shopify’s updates, as this feature could be added in the future.
Let me know if you need more insights or alternatives!