There is no way to register a unit in the application, the model and ID (IMEI) of which coincide with an existing unit in neither the same nor in different accounts.
Otherwise, the user would not have sufficient security in the data. Since any outsider who knows the IMEI and the tracker model and the application you are using (for example, the seller if he sells the tracker and advises you on the application) could register a unit in the same application as you and watch your movement. Therefore, there is no such possibility in the application.
If you are considering the possibility of creating subaccounts from your main account, for example, for employees, if you use trackers for business purposes, could you tell us in more detail what functions in this case would you like to see?