 You can create subfolders under your library. For example, you can see I have art and symbolism. Perhaps you want to make a folder for a specific project. Let's say I'm writing a research paper on sloths. I'm going to select my library, choose the icon that looks like a folder, which is New Collection, and give it a name. Now to add items into my new folder, I go to my library, and I can click and drag an item, and just drop it into my new folder. Now you can see when I select that folder, that item appears. It's going to stay in my main library too. To delete a folder, simply select it from the menu, right-click, and choose Delete Collection.