In the course of data sharing you may find yourself in a situation when some of your linked devices stay offline and aren’t actually used, or if a remote device suffers hardware failure and loses Sync installation.
Sync has a feature which lets you clear those offline devices so that they don’t clutter up your device list. Clearing doesn’t unlink your device - it just hides it from view, therefore, if a cleared device ever goes back online, it will reappear on the My Devices list allowing you to continue sharing data as before.
To clear an offline device, go to My Devices > Info of the device you would like to clear > Thee dots menu -> Hide device: