Final answer:
The ability to add or remove lines within a cart during an activation flow generally depends on the design of the specific e-commerce platform or service provider's system, but most modern systems allow these changes for a better user experience.
Step-by-step explanation:
It pertains to the user interface and functionality of an online activation flow, potentially for a service or software where one may need to add or remove items from a cart or plan. The answer to whether you can add or remove lines within your cart during the activation flow without starting over depends significantly on the specific system or website's capabilities.
Typically, modern e-commerce platforms and service providers are designed to allow users to edit their cart contents during the activation process without needing to restart from the beginning. This feature is implemented to enhance the user experience by making it more convenient and flexible.