When ADOMs are enabled, FortiManager includes default ADOMs for specific types of devices. When you add one or more of these devices to FortiManager, the devices are automatically added to the appropriate ADOM, and the ADOM becomes selectable. When a default ADOM contains no devices, the ADOM is not selectable.
For example, when you add a FortiClient EMS device to the FortiManager, the FortiClient EMS device is automatically added to the default FortiClient ADOM. After the FortiClient ADOM contains a FortiClient EMS device, the FortiClient ADOM is selectable when you log into FortiManager or when you switch between ADOMs.
You can view all of the ADOMs, including default ADOMs without devices, on the System Settings > All ADOMs pane.