pre_network_site_new_created_user
Action Hook: Fires immediately before a new user is created via the network site-new.php page.
Source: wp-admin/network/site-new.php:117
network_site_new_created_user
Action Hook: Fires after a new user has been created via the network site-new.php page.
Source: wp-admin/network/site-new.php:136
network_site_new_form
Action Hook: Fires at the end of the new site form in network admin.
Source: wp-admin/network/site-new.php:313