The superadmin group allows to navigate every project, run and analysis on nG6, hidden or not, with admin rights.
There is a new table in the admin section ( Administration > Admin management ) that allow superadmins to add and remove users to and from the superadmin group.
The group's key is NEVER written directly in the source code, allowing an easier deployment for production use.
The only requirement outside of the source deployment is to create a group with title = 'ng6_superadmin'. For additional informations, check the SQL file.