WordPress multisite Super Admin: How this record with with so high permissions is defined? Are any user role or user capabilities used for that?
For the 1st glance, we have a quick answer. Yes, of course, just look at these user capabilities set: 'create_sites', 'manage_sites', 'manage_network', 'manage_network_options', 'manage_network_plugins', 'manage_network_themes', 'manage_network_users'
. These capabilities definitely differentiate local administrator from the network one. And we will be right. If to add capabilities listed above to the local admin role, e.g. built-in ‘Administrator’ of the 1st, main site of the network, user with such role will get limited Super Admin privileges for the whole network. But it is not the full story. Read more WordPress multisite Super Admin privilege