I checked the board for similar questions, but the answer was from 2008 and it said to just copy the folder to a new location, open the Robohelp file & go to "file> rename file".That is not an option in Robohelp 2019. There is no "save as", so what is the best way to duplicate a project as a template?
Looks like it is much the same.
Copy the folder in File Explorer. Rename the rhpj file if you want to. Open the project and go to Project Settings to change the Project Title.
It was a quick check but it appears to work just fine.
See www.grainge.org for free RoboHelp and Authoring information.