In ManagementStudio Deployment Units (DUs) are designed to enable the scheduling of users, devices or some other asset type for change or migration. It’s common to manage tranches of migrations by location or department. ManagementStudio supports multiple DUs (e.g. one per location/department), but it’s also possible to simplify the management in ManagementStudio by using a single DU for the entire project.
See here for details on how to achieve this.