function add_bike_details($bike_details) {

    $bike_details['label'] = "Bike Details:";

}

add_action('woocommerce_admin_booking_data_after_booking_details', 'admin_booking_data_after_booking_details_callback', 10, 1 );

function admin_booking_data_after_booking_details_callback( $booking_id ) {
    // Get the WC_Booking instance Object
    $booking = get_wc_booking( $booking_id );

    // Your code come here
}