You can view all devices that have connected to the server from the settings. This will include both currently connected devices and any that have connected in the past. At the moment this page is really only useful to see connected devices and what users are registered to them.
The only option available at the moment is editing the display name. This can be useful for adding names that can better identify devices. The original name will stay visible in the options if you modify the value.
If you don't want to keep old devices on the server you can remove them from this page. Please note that if a device connects again it will show up here. Removing a device does not hide the device forever, it simply cleans out old entries.