Example of how to replace the function used to add the 'Ticket Notice' and 'Ticket icon' to the Registration and Transaction list tables.

ee_tw_custom_ticket_notice_trigger.php

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



function ee_tw_custom_ticket_notice_trigger( $action_items, $item, EE_Admin_List_Table $list_table ) {
    // First, remove the regular filter for the ticket notice/ticket icon.
    remove_filter(
        'FHEE__EE_Admin_List_Table___action_string__action_items',
        array('EED_Ticketing', 'resend_ticket_notice_trigger'),
        10
    );

    // Now re-do the ticket notice/tickets icon with a custom version
    if (! EEH_MSG_Template::is_mt_active('ticket_notice')
        && ! EEH_MSG_Template::is_mt_active('ticketing')
    ) {
        return $action_items;
    }
    if ($list_table instanceof EE_Registrations_List_Table && $item instanceof EE_Registration) {
        $resend_tkt_notice_lnk = '';
        // only display resend ticket notice link IF the registration is approved.
        if ($item->is_approved()) {
            $resend_ticket_notice_url = EEH_URL::add_query_args_and_nonce(
                array(
                    'action'  => 'resend_ticket_notice',
                    '_REG_ID' => $item->ID(),
                ),
                admin_url('admin.php?page=espresso_registrations')
            );
            $resend_tkt_notice_lnk = EEH_MSG_Template::is_mt_active('ticket_notice')
                                     && EE_Registry::instance()->CAP->current_user_can(
                                         'ee_send_message',
                                         'espresso_registrations_resend_ticket_notice',
                                         $item->ID()
                                     ) ? 
            '<li>
                <a href="' . $resend_ticket_notice_url . '" title="' . esc_html__('Resend Ticket Notice', 'event_espresso') . '"'
                            . ' class="tiny-text">
                    <div class="dashicons dashicons-email"></div>
                </a>
            </li>'
            : '';
        }
        $display_ticket_notice_url = EED_Ticketing::getTicketUrl($item);
        $display_tkt_notice_lnk = ! empty($display_ticket_notice_url)
                                  && EEH_MSG_Template::is_mt_active('ticketing')
                                  && EE_Registry::instance()->CAP->current_user_can(
                                      'ee_send_message',
                                      'espresso_registrations_display_ticket',
                                      $item->ID()
                                  ) ? 
            '<li>
                <a target="_blank" href="' . $display_ticket_notice_url . '"'
                            . ' title="' . esc_html__('Display Ticket for Registration', 'event_espresso') . '" class="tiny-text">
                    <div class="dashicons dashicons-tickets-alt"></div>
                </a>
            </li>'
            : '';
        return $action_items . $resend_tkt_notice_lnk . $display_tkt_notice_lnk;
    }
    if ($list_table instanceof EE_Admin_Transactions_List_Table && $item instanceof EE_Transaction) {
        $display_ticket_notice_url = EED_Ticketing::getTransactionTicketsUrl($item->primary_registration(), true);
        $display_tkt_notice_lnk = EEH_MSG_Template::is_mt_active('ticketing')
                                  && EE_Registry::instance()->CAP->current_user_can(
                                      'ee_send_message',
                                      'espresso_transactions_display_ticket',
                                      $item->ID()
                                  ) ? 
            '<li>
                <a target="_blank" href="' . $display_ticket_notice_url . '"'
                            . ' title="' . esc_html__('Display Ticket for Registration', 'event_espresso') . '" class="tiny-text">
                    <div class="dashicons dashicons-tickets-alt"></div>
                </a>
            </li>'
            : '';
        return $action_items . $display_tkt_notice_lnk;
    }
    return $action_items;
}
add_filter('FHEE__EE_Admin_List_Table___action_string__action_items', 'ee_tw_custom_ticket_notice_trigger', 9, 3);