One useful feature on macOS is an option called “Duplicate” in the right click menu of the Finder*. This creates a copy of the file in the same folder with the word “copy” appended to the end of the filename. e.g. “My document.pdf” has a copy called “My document copy.pdf”.
Can this be added to Files?
Personally I use it all the time.
*macOS Finder also has a copy option in the right click menu which functions the same as Gnome Files.
Why do you need a dedicated duplication button when can just copy and paste in the same place?
because on macOS it’s 3 clicks to duplicate a file, on Gnome it’s 6 clicks.
Just being less clicks is not always a useful usecase if it regresses other things like space and menu size. It need to be of enough importance that extra space for an action already possible through other means is justified. An example of that is the new folder in button in the file chooser.
That duplicate action is very good idea that improves working with files in that way. It could be optional menu item to enable in Files preferences like for now ‘Create link’ and ‘Delete permanently’.
For example, Nemo from Cinnamon has this