1. SAP Help Portal: RISE with SAP S/4HANA Cloud, Private Edition, System Transition Workbench. The official documentation states, "The RISE with SAP S/4HANA Cloud, private edition, system transition workbench is your central entry point to start, plan, and execute your transition project to the private cloud." This directly validates that it is a single point of entry for migration. (See the "Overview" section).
2. SAP Community Blog: Introducing the new RISE with SAP S/4HANA Cloud, private edition, system transition workbench. This official blog post describes the tool as a "single, central place for you to manage your transition project" and highlights its role in providing a "guided journey" for the migration process. (Published by SAP employees, e.g., Product Management).