[Smart SEO Export Fields] Lets you export other custom fields to include in bulk editing

smart_seo_export_fields.php

<?php
add_filter( 'smart_seo_export_fields', 'child_export_other_custom_fields', 8, 1 );
function child_export_other_custom_fields( $fields ){
	$fields[] = '_custom_field_name'; 		// _custom_field_name will exported to CSV as well
	$fields[] = '_another_custom_field';	// _another_custom_field will exported to CSV as well
	return $fields;
}
?>