Collections and subcollections are essentially digital folders that allow for you to organize your sources in your Mendeley library. Collections are listed in alphabetical order underneath the Collections heading. You can access the complete list of references in your library by clicking the "All References" tab on the left side of your library. Placing a source into multiple collections or subcollections in your library. Mendeley also has several default "Smart" collections including: "Recently Added", "Recently Read", "Favorites", "My Publications", "Unsorted", "Duplicates" and "Trash". These appear at the top of your library.
In the desktop application, you can add a collection by clicking "Create Collection" within the left toolbar under Collections. You can add a subcollection by right-clicking on a collection and selecting "Add Subcollection".
Mendeley has a functionality to add tags to your references that you can filter and search for later. To add a tag, click your reference and navigate to the details window, which usually appears on the right side. You can then scroll to the "Added by Me" heading, and "Tags" will be listed underneath. You can add tags by clicking the plus button.
