I’m trying to get a grasp on Checkout Extensibility for Shopify Plus. From what I’m understanding, Shopify is restricting the ability to run javascript or CSS within the checkout process and now everything has to run through an app. But I’m having trouble finding docs for actually creating an app for checkout. I found a list of apps that are available, but am not seeing anything about creating a custom app, which is what I assume I’d need to do to run custom code.
Are checkout apps limited to specific partners right now?
For existing scripts I’m using (from third parties) in the checkout flow, do those all have to be converted to apps by their developers in order to retain that functionality?