Cloning a Lightbox allows you to make a new copy of an existing Lightbox. You can leave the original version (and any existing connections to it) intact while making changes to the permissions, organizational structure, number of assets, or workflows of the new version.
Since Mediagraph does not allow you to move Lightboxes from one Project to another, you must first clone the Lightbox, then move the new copy to the desired Project using Rearrange Mode.
Note that the assets contained in the original Lightbox will not be duplicated. Any changes made on an asset level within the cloned Lightbox (metadata or access restrictions, for example) will apply to the assets wherever they are visible across your Mediagraph account.