For some websites, you would need several Joomla menus to be identical. By identical, we mean that they both are or the same type, sharing the same style and the same behavior. Instead of setting both of these menus up and copying all the parameters, you can select one of the “Copy from …” options and all parameters for this menu will be copied from the selected menu.
This will also save your time if you decide to change some menu parameters later. Instead of changing the same parameter for all menus, you can change it once and the parameter will be updated in all copied menus as well.
Note that it’s not recommended to use the Off-canvas menu type multiple times on the same page. Therefore, it’s not recommended to copy the menu settings from menu that uses the Off-canvas menu type.