In the Rename, Move and Copy files we can copy a file or we can copy and point to the new file, but there is no option to copy and have both files in the database.
Here is why this option would be useful.
You could copy your Eggs Benedict file ("My Documents\Recipes\Eggs and Cheese\Eggs Benedict.txt") that is already all tagged with genre and keywords and everything, keep the directory the same and change the filename to Eggs Florentine for the new copy. Select the "copy (include copy in database)" option and bingo: all you need to do is open the new file and modify the text. You've just saved yourself from having to go find the file on your computer, import it and reassign all tags.
Or you could quickly copy a picture of your dog to make webfriendly for Facebook. Since both files would be in your database with all the same tags etc you could find it easily and modify one of them as you please (tags, change resolutions, etc).