Are there customize trigger for checkout without Plus(checkout.liquid)?

[ynishi]

Hi there,

I'm planning an app to publish multiple dist website for tracking when checkout with custom values via javascript.

It seemed to resolve it via checkout.liquid and scriptTag call in it, but it is needed Plus plan.

Other, checkout webhook is available, but it looks like custom field is not supported.

I think solution, the setting from admin provided app, store app's side, and sub webhook and make something and publish.

Are there good idea or best practice work with checkout?