I currently have 300+ server each on a different subnet.
It is possible to import devices using the "Inventory for External" with the credentials assigned to them. However in order to deploy a Robot and get the WMI information, they must be added via the "Discovery Wizard". Each IP address has to be entered manually.
Since the imported devices can automatically show up with the IP address and credentials it makes sense for there to be an option to select the devices and click the Actions to automatically have the details for those devices added to a discovery schedule.