The new Fanfiction tab works like this:
Each of the pages on it (For example, Rising Sun) lists a series of blogs about it. It knows which blogs to show because it chooses only the blogs from a particular category (In this example, the category is called "Rising Sun".)
When you make a new addition to your series, you can add the corresponding category to your blog.
Current categories: Rising Sun Battle for Run Castle Secrets A Legend from the Planet
If you want to know how to make a blog listing page, check the video I made. The link on the second tab is https://run.fandom.com/wiki/Special:CreateBlogListingPage.