The best way to identify the configuration changes that need to be moved into production is to leverage the Setup Audit Trail to review the changes made by the departed Administrator and identify which changes should be added to the Change Set. The Setup Audit Trail is a feature that tracks the recent setup changes that you and other administrators have made to your org. The Setup Audit Trail can show up to 180 days of history and can be downloaded as a CSV file. The Setup Audit Trail can help the developer to find out what configuration changes were made by the former administrator, such as creating or modifying objects, fields, workflows, processes, flows, etc. The developer can then use this information to complete the Change Set and deploy it to production . Reference: [View Setup Audit Trail], [Change Sets]