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 Preferences > Identity > MyDevices > Info of the device you would like to clear > Thee dots menu > Hide this device: