That makes sense. In Discourse terminology what you want to do is export a category. That is possible with the command line tools that are described in the topic that you linked to. On our hosted sites you do not have access to the site’s backend, so this will not be possible for you.
One thing to note, on our hosted sites you do have complete access to the Discourse API, but I’m not sure that will help for your case.
If you are on our Business plan, your best approach would be to use the Data Explorer plugin. We can help you to write a query for that if you’re stuck. If your site is on our Standard plan, get in touch with us through the support email address that’s on your admin dashboard. We’ll see what we can do to help.