This hook allows you to add the custom content in the trips itinerary page just below the trips listing section.

Source

File : /templates/archive-itineraries.php

Example :

function prefix_wp_travel_archive_listing_sidebar() {
    esc_html_e( 'This is the content added using this hook', 'text-domain' );
}
add_action( 'wp_travel_archive_listing_sidebar', 'prefix_wp_travel_archive_listing_sidebar' );