How to Duplicate Items on Your MacBook with El Capitan
If you need more than one copy of the same item in a folder on your MacBook, use the El Capitan Duplicate command. Duplicate is a handy command when you want to edit a document but want to ensure that the original document stays pristine, no matter what. You can just create a duplicate and edit that file instead.
To use Duplicate, you can
Click an item to select it and then choose File → Duplicate.
Right-click the item and choose Duplicate from the menu.
Hold down the Option key and drag the original item to another spot in the same window. When you release the trackpad button, the duplicate file appears like magic!
The duplicate item has the word copy appended to its name. A second copy is named copy2, a third is copy3, and so on.
Duplicating a folder also duplicates all the contents of that folder. Therefore, creating a duplicate folder can take some time if the original folder was stuffed full (or contained files several hundred megabytes or larger in size). The duplicate folder has copy appended to its name, but the contents of the duplicate folder keep their original names.