Zotero

Organize your library by creating folders, which are called collections in Zotero. You might find it helpful to organize items by course, theme, or topic. Create a new collection by choosing the "New Collection" icon or right-clicking on "My Library" and choosing "New Collection." 

You can also create subfolders by right-clicking on a collection and choosing "New Subcollection." Right-clicking on a collection will also give you the option to rename or delete a collection. 

You can add notes and tags to items in your Zotero library. There are tabs for notes and tags in the right-hand pane next to the "Info" tab. 

Tags provide another way for you to organize your library. You can search by tags using the "All Fields & Tags" search box. Some databases automatically include tags (or keywords) when you add an item to your library. You can disable automatic tagging in Zotero's General preferences.