You can set up an organization and its members in Users & System Administration.
After adding or changing organizations, you can assign users to them.
You can also use a CSV file to change the settings in bulk.
For details, refer to how to add and edit data in bulk, such as users and organizations.
By using the tentative structure of the organization, you can set a new structure for the organization in advance and apply it to the operational environment at the specified date and time.

This reduces the maintenance burden for user administration.
For details, refer to tentative organization.