The 1C:Enterprise platform automatically transforms applications from desktop to mobile so 1C developers do not operate with such native mobile concepts like DeviceToken directly. Why do you need it?
Take a look at DeliverableNotificationSubscriberID in Syntax Assistant, the DeviceID property. To send a notification use the Send method of DeliverableNotificationSendManager
To get the device ID, you can use ReceiveNotificationSubscriberID method on a device and pass it to the server. Please remember, that device ID for some reason is not a constant so you have to get and update it time to time. On start, for example.
I tried to use this function (devID = DeliverableNotifications.ReceiveNotificationSubscriberID() in ManagedApplicationModule OnStart(), but it generates error "Error calling context method".
I am using 8.3.8.58 on mobile and 8.3.8.2332 on desktop.