How does the Shopify Digital Downloads app add checkout link automatically?

Shopify Partner
29 0 3

In the last screenshot on the App listing page it shows a Settings screen with a checkbox to add the download link to the checkout page:


How do they do this? I cannot find any API for accessing the "Additional scripts" in Settings > Checkout. 


Right now I have a help article to guide merchants to install my code snippet in Settings, but it would be huge if I could simply enable this automatically.




Screen Shot 2020-04-27 at 11.05.11 AM.png