The documentation for favorites says:
Ctrl+C and Ctrl+V can be used to copy and paste Favorites. They can be used to copy a Favorite from one section and paste it into another.
But the keyboard shortcuts Ctrl+C and Ctrl+V have no effect in the Favorites dialog, neither in the current version (v13.5) nor in older versions (tried with v11.3 from 2021).
It's just a minor problem and fortunately there is a workaround:
Copying and pasting in the Favorites dialog can be done via the context menu.