Updating session
Modifying Cart Items, Amounts, and Discounts
When the items of a cart, total amount or discounts are changed on a previously created session, the session must be updated with the newest changes.
To update the session, first it needs to be locked. Locking the session is done by using the Checkout Web SDK. When the session is locked, updating the session can commence. Documentation for updating the session can be found here
It's not possible to update a session after it's been completed.