So let me summarize what we have so far. You can get something like what TT wants by first going under your preferences → notifications → categories.
Add all categories that you’re interested in (which will probably be all) to the first item at the top, “Watched”.
Save your changes.
Now when you want to see your “unread”, go to the “unread” tab at the top. You may need to change the “Activity” sort order if you have a lot of “unread” posts.
When you want to mark everything as read, click on the surprised hamburger “topics” at the left of the posts.
Select “Select all”.
Then click on “Dismiss…” over on the right hand side.
There will be a dialog making sure this is what you want to do. Inside that dialog select “Stop tracking…” .
