Here is the guidance by app type. Please check the following.
Web Browser Version
Duplicating a manual (Web Browser Version)
https://teachme.jp/8/manuals/4929576
Restoring and duplicating a manual from edit history (Web Browser Version)
https://teachme.jp/8/manuals/34160292
Mobile App
Duplicating a manual (Mobile App)
https://teachme.jp/8/manuals/3204665