update_wpmu_options
Action Hook: Fires after the network options are updated.
Source: wp-admin/network/settings.php:132
mu_menu_items
Filter Hook: Filters available network-wide administration menu options.
Source: wp-admin/network/settings.php:497
wpmu_options
Action Hook: Fires at the end of the Network Settings form, before the submit button.
Source: wp-admin/network/settings.php:531