Gravity Forms Email Fields Notification Admin Hook

gform_email_fields_notification_admin.php

add_filter("gform_email_fields_notification_admin", 'add_field_to_email_list', 10, 2);

// This filter add/remove fields from the list of email fields that get displayed on the Notification edit page when configuring 
// the "Send To Field".

add_filter("gform_email_fields_notification_admin", 'add_field_to_email_list', 10, 2);
function add_field_to_email_list($field_list, $form){

   //Adds field with ID=1 to the list of email fields
   foreach($form["fields"] as $field){
       if($field["id"] == "1")
           $field_list[] = $field;
   }

   return $field_list;
}