Main-ActionCenter is a workflow that allows you to create and manage Document Understanding actions in Action Center, which is a web application that enables human intervention in automation processes. You can use Main-ActionCenter when you want to test your Document Understanding process locally, or when you want to implement an attended process that requires human validation or classification of documents. Main- ActionCenter is not recommended for unattended processes, as they do not involve human interaction.
References: Action Center - Document Understanding activities, Document Understanding Process 22.10 now in General Availability!, How to Start a UiPath Document Understanding Project