I am sorry I couldn’t be of any help to you. I was a bit mislead as in your OP you wrote about “unread topics” which are treated by Discourse as “New” which means “not read by you so far at all”. That is why I have been asking repeatedly if your focus are those topics you did not read at all or those you read earlier but with new posts after your last visit.
Nevertheless the settings I described are the tools Discourse offers you for the selection of the topics you are looking for. Whenever visiting your subcat “Nederland” you will be provided automatically with 3 topic lists which are
- Latest = a chronological list of all topics in your subcat notwithstanding if you have read them or not
- New = all topics created since your last visit (or out of any other period according to your setting)
- Unread= all topics read earlier but with new posts
So after checking out the “New” and “Unread” you can dismiss those you do not want to read and that’s it. Next time you visit the same procedure starts again. Those you are looking for are the “New” and “Unread” - I am sorry these are split in 2 lists but that is how Discourse does it.
If no “New” or “Unread” button to open the respective list is shown in the headline (left of the button “Latest”) there are no new or unread topics waiting for you. It is as simple as that.
Last hint: The filter for “Unread” topics again depends on your preference settings. To be sure that every topic with new posts will be filtered into this list the most simply way is to set the whole subcategory to “tracking” (or even “watching”) as described by @Tordanik in post #13.