This is a helper variable that defines the registry key under which Windows Explorer folder paths are stored for the current user. It is used by other variables to retrieve shell folder paths for the current user.
You can refer to this variable as <ShellFoldersCU>. Because it is a registry path, it is typically used as <@<ShellFoldersCU>\...additional path...>. Do not change its value; it has been carefully configured for cross-platform compatibility.