Could you please clarify if you mean that you need to export a list of all the Host that are connected to your RU Server? If this is the case, you can find your Server's address books saved in the data folder in the following location: C:\Program Files (x86)\Remote Utilities - Server\. If you mean that you want to set up your Server to automatically add any Host that contacted your Server, then you can set up the auto-import feature as described in this tutorial.
Additionally, can I export the station ID from its Windows registry or from a local folder ?.
Yes, of course, you can find the Host's Internet-ID code in its registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Usoris\Remote Utilities Host\.
Unfortunately, it's not possible to force Agent to store its settings from the registry key in the plain text format. The Host/Agent registry keys contains XML encoded as UTF-8. This binary data is not encrypted, it's just encoded as Hex code. Therefore, you only need to convert Hex code to UTF-8, and read the XML with data using any "Hex to UTF-8" online converter. Alternatively, the Internet-ID code is available as a plain text in the Agent's window itself.