When creating an event this sets the “Personal Information” question group checkbox checked by default for the “Questions for Additional Registrants” section, so that the administrator won’t forget to tick the box.

ee_check_additional_questions_default.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_action( 
  'FHEE__EE_Admin_Page___load_page_dependencies__after_load__espresso_events__create_new',
  'ee_custom_checkboxes_for_additional_question_groups_hook' 
);
function ee_custom_checkboxes_for_additional_question_groups_hook() {
  add_action(
    'AHEE_event_editor_questions_notice',
    'ee_custom_checkboxes_for_additional_question_groups'
  );
}
function ee_custom_checkboxes_for_additional_question_groups() {
  echo '<script>jQuery( document ).ready(function($) {
      $("#espresso_events_Registration_Form_Hooks_Extend_additional_questions_metabox input[value=\'1\']")
      .prop( "checked", true );
    });</script>';
}