Zedna Maintenance Mode
You can lock whole website by setting it under maintenance.
Select roles who applies maintenance mode
Set a redirect to login page
Edit a maintenance message in wysiwyg editor including media
zedna-maintenance-mode folder to the
Activate the plugin through the ‘Plugins’ menu in WordPress
Can i set maintenance mode for Super admin?
On single site yes, it’s just administrator, but on multisite no as there is no need to have maintenancefor the biggest developer in da house.