What should you edit to ensure a new form submits an action in the existing Cart controller?

To ensure that a new form submits an action in the existing Cart controller, it is essential to add actions to the XML form definition. This is because the XML form definition acts as a blueprint that specifies the actions associated with forms, including how they interact with controllers and what processing should occur when they are submitted. By defining the actions in this XML file, the new form will be properly linked to the Cart controller's functionality and be able to handle operations like adding items to the cart, updating quantities, or removing items.

This choice is fundamental in establishing the communication between the front-end form and the back-end logic contained in the controller, ensuring that user submissions are processed correctly. When forms are defined correctly within the XML and linked to the appropriate controller actions, it facilitates seamless user interactions in the e-commerce environment managed by Salesforce Commerce Cloud.