Does the In-app Script allow me to pass a value to the Custom Fields?
In Chargebee, it is possible to pre-fill the email using either the drop-in script or by using Chargebee's API.
Via Drop-in Script
Once the custom field is created, all the parameters for the Customer can be passed using the setCustomer function. This information will be passed to checkout and will be prefilled - including the custom field.
You can use the SetCustomdata function to pass the Subscription level custom fields. To know more about the Checkout page script.
Please refer to the example shown under drop-in script customizations from here.
Custom field parameters start only with ‘cf’ as shown in the image below
Sample Custom filed format for which the parameters need to be passed.
You can view the custom fields format from this link, and navigate to Checkout new subscription > Input parameter > Customer.
More on API docs for hosted pages here.
via Hosted page URL
In a hosted page URL for a plan, you can pass the custom field as a parameter and embed it in the checkout button on your page.
Refer to the Pre-filling/Passing custom fields to hosted pages (via Plan URL) document to know more.
You can also read more about Custom Fields.