Tags provide a very flexible way to organize your collected articles.
Add words of your choosing in the Tags field on the Details screen.
Use Mendeley Desktop search to retrieve articles by tags. Enter the search using the following format.
tags:your topic, your second topic
Folders and subfolders are another option for organizing your collected articles.
Click on the Create Folder option in the left side bar, enter a folder name, and then drag and drop relevant articles into the folder. One article can be put in multiple folders. Any folder can be dragged onto an existing folder to create a subfolder. Subfolders can have subfolders.
It is important to keep only one instance of an article in your Mendeley database. Multiple instances of the same article can be confusing when you are citing while writing. It is a good idea to check your database for duplicates before you start to write a new document.
Click on Tools / Check for Duplicates
Review duplicates that are found
If they are true duplicates, delete one or merge the records.