You can use tags to name a group of devices based on a business unit or a physical location. For example, if you tag a device with third floor, and then search for third floor, all devices with that tag show up.
From the customer view in https://admin.webex.com, go to Devices, and select the device you want to tag.
Select Tags in the panel that opens on the right, add a tag, and click outside the field to apply the tag.
The tag doesn't appear in the device list, only the overview of a device. However, you can use tags in a filter list to find devices with that tag.