Why are some topics unpinned to me?

Oh that’s great!

And I saw this as well, which is probably a bit more useful and obvious, inside the topic itself:

But bookmarks can become a bit messy, I think. At least when you are inside a category, if it’s something important and it’s pinned, you know where to find it. Now if you have 100 bookmarks…
Unless there’s a way to create categories for bookmarks to keep the organize? Or folders? Similar to how Facebook and Instagram allows collections of saved posts.