Force the confirm_email question type to be visible when editing the Address Information system question group.

tw_ee_force_confirm_email_to_show.php

<?php // Please do not include the opening PHP tag if you already have one.

// This snippet forces the 'confirm_email' question type to be visible on the Address Information system question.
// Add this snippet to your site and go to Event Espresso -> Registrations Form -> Question Groups -> Address information.
// Find the 'Confirm Email' question, UNcheck it so it is no longer set in that question group and save.
// Now remove this snippet again.
add_filter('FHEE__EEM_Question__system_questions_allowed_in_system_question_group__return', 'tw_ee_force_confirm_email_to_show', 10, 2);
function tw_ee_force_confirm_email_to_show($question_system_ids, $system_question_group_id) {
	if( $system_question_group_id === EEM_Question_Group::system_address ) {
		$question_system_ids[] = EEM_Attendee::system_question_email_confirm;
	}
	return $question_system_ids;
}