List of default fields in Additional Charges and their corresponding keys from the array

• subtotal => ‘wpcpq_subtotal’
• freight => ‘freight’
• fuel =>  ‘fuel’
• stops =>  ‘stops’
• layover =>  ‘layover’

Add field for additional charges

add_filter( 'wpcpq_package_additional_charges', 'add_wpcpq_package_charges' );
function add_wpcpq_package_charges( $package_additional_fields ){
$package_additional_fields['driver'] = array(
					'label' => 'Driver',
					'field' => 'number',
					'required' => false,
					);
	return $package_additional_fields;
}

Update field for additional charges

add_filter( 'wpcpq_package_additional_charges', 'add_wpcpq_package_charges' );
function add_wpcpq_package_charges( $package_additional_fields ){
$package_additional_fields['freight'] = array(
											'label' => 'Custom Freight Label',
											'field' => 'number',
											'required' => false,
										);
	return $package_additional_fields;
}

Remove field from default additional charges

add_filter( 'wpcpq_package_additional_charges', 'add_wpcpq_package_charges' );
function add_wpcpq_package_charges( $package_additional_fields ){
	unset ($package_additional_fields['freight']);
        unset ($package_additional_fields['wpcpq_subtotal']);</pre>
<pre>	return $package_additional_fields;
}