Below screenshot shows the section wherein hooks will be added.

Add the following codes in your theme’s functions.php file.

Section at the top of results page

add_action('wpcargo_before_track_details', 'custom_wpcargo_before_track_details' );
function custom_wpcargo_before_track_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_before_track_details</strong></p>';
}

Section to add in header content

add_action('wpcargo_track_header_details', 'custom_wpcargo_track_header_details' );
function custom_wpcargo_track_header_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_track_header_details</strong></p>';
}

Section after the header details

add_action('wpcargo_track_after_header_details', 'custom_wpcargo_track_after_header_details' );
function custom_wpcargo_track_after_header_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_track_after_header_details</strong></p>';
}

Section to add in shipper/receiver content

add_action('wpcargo_track_shipper_details', 'custom_wpcargo_track_shipper_details' );
function custom_wpcargo_track_shipper_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_track_shipper_details</strong></p>';
}

Section before shipment details

add_action('wpcargo_before_shipment_details', 'custom_wpcargo_before_shipment_details' );
function custom_wpcargo_before_shipment_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_before_shipment_details</strong></p>';
}

Section after shipment details

add_action('wpcargo_track_shipment_details', 'custom_wpcargo_track_shipment_details' );
function custom_wpcargo_track_shipment_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_track_shipment_details</strong></p>';
}

Section after shipment history

add_action('wpcargo_after_track_details', 'custom_wpcargo_after_track_details' );	
function custom_wpcargo_after_track_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_after_track_details</strong></p>';
}

Section after package table

add_action('wpcargo_after_package_details', 'custom_wpcargo_after_package_details' );
function custom_wpcargo_after_package_details( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_after_package_details</strong></p>';
}

Section after package totals

add_action('wpcargo_after_package_totals', 'custom_wpcargo_after_package_totals' );
function custom_wpcargo_after_package_totals( $shipment ){
	echo '<p style="color: #F44336;"><strong>wpcargo_after_package_totals</strong></p>';
}

How to display my custom dynamic field on the results

The variable $shipment returns value of shipment ID and shipment number. Copy and paste below codes on your child theme functions.php file. Replace the custom_meta_field with the name of your meta key to display its value.

add_action('wpcargo_track_shipment_details', 'custom_wpcargo_track_shipment_details' );
function custom_wpcargo_track_shipment_details( $shipment ){
	$shipment_id = $shipment->ID;
	$custom_meta_field = get_post_meta( $shipment_id, 'custom_meta_field', true );
	echo '<p style="color: #F44336;"><strong>Custom meta field: </strong>'.$custom_meta_field.'</p>';
}