In iOS or macOS Contacts App, I would like to duplicate a contact. What is the easyest way to do this?
VCF files are just text files, so you can edit them in every text editor.


Right-click on VCF file
Select "Open with" and then "Textedit.app"
Change whatever field you want to change (N and FN are typical fields to change if you want to change the name)
Use "Save as" to save with a new file name


PS: See https://en.wikipedia.org/wiki/VCard#Properties for details about the different fields. Not all of them may be supported by Contacts though.