I tried the plugin “Happy Files” (https://happyfiles.io/) to organize the media library on a big site but unfortunately Happy Files does not work inside Cornerstone. Even with the latest version, which has some tweaks to force the Happy Files interface to get loaded (The new “Enforce loading” setting under Settings > HappyFiles ensures HappyFiles is loaded throughout the admin area and/or frontend for logged-in users. This only enable to use HappyFiles with third-party plugins and themes that are not officially supported (e.g. some page builders, etc.)), it does not work 
Is there a documentation how to implement an external plugin in Cornerstone?
