Detailed instructions for creating a new Zapp version can be found here.
To clone a Zapp, go to the Zapp's version list page. Click on the three dots icon on the right hand side of the version you wish to clone.
Choose "Create a New Zapp from Version" from the dropdown menu.
A confirmation message will display.
Go to the main Zapps page. The cloned Zapp will be listed. Its name will follow this format: Previous Zapp Name (clone of Previous Zapp ID).