How can I upgrade to Checkout Extensibility?
This feature can be separately activated for the checkout steps (contact, shipping, and payment) and the thank you/order status page (OSP).
Stores that only want the one-page checkout need to upgrade for the checkout steps.
Stores that want to develop an app for these steps or use Shopify’s layout for the thank you/OSP must activate it for the thank you/OSP page, as well.
1. First, navigate to Settings > Checkout.
2. Create a draft and then click Publish.
To learn more about, you can read our article on Shopify Checkout Extensibility.