"The purpose of the improve value chain activity is to ensure continual improvement of products, services, and practices across all value chain activities and the four dimensions of service management."
https://www.symphonysummit.com/products/defining-industry-terms-itsm-itil-itil4/#:~:text=Improve%20% E2%80%93%E2%80%9CThe%20purpose%20of%20the,four%20dimensions%20of%20service%
20management.%E2%80%9D

Reference: https://www.bmc.com/blogs/itil-key-terms/

The change schedule is used to help plan changes, assist in communication, avoid conflicts, and assign resources. It can also be used after changes have been deployed to provide information needed for incident management, problem management, and improvement planning
https://www.bmc.com/blogs/itil-change-enablement/#:~:text=The%20change%20schedule%20is%20used,proble

management