woocommerce-customer-order-csv-export-renaming-removing-reordering-columns.php

<?php

// rename a column
function wc_csv_export_rename_column( $column_headers ) {

	// rename the order_notes column to notes
	// make sure to not change the key (`order_notes`) in this case
	// as this matches the column to the relevant data
	// simply change the value of the array to change the column header that's exported
	$column_headers['order_notes'] = 'Notes'; 
 
	return $column_headers;
}
add_filter( 'wc_customer_order_csv_export_order_headers', 'wc_csv_export_rename_column' );

// remove a column
function wc_csv_export_remove_column( $column_headers ) {

	// the list of column keys can be found in class-wc-customer-order-csv-export-generator.php
	unset( $column_headers['coupon_items'] );
 
	return $column_headers;
}
add_filter( 'wc_customer_order_csv_export_order_headers', 'wc_csv_export_remove_column' );

// reorder columns
function wc_csv_export_reorder_columns( $column_headers ) {

	// remove order total from the original set of column headers, otherwise it will be duplicated
	unset( $column_headers['order_total'] );

	$new_column_headers = array();
	
	foreach ( $column_headers as $column_key => $column_name ) {
		
		$new_column_headers[ $column_key ] = $column_name;
		
		if ( 'order_number' == $column_key ) {
			
			// add order total immediately after order_number
			$new_column_headers['order_total'] = 'order_total';
		}
	}
	
	return $new_column_headers;
}
add_filter( 'wc_customer_order_csv_export_order_headers', 'wc_csv_export_reorder_columns' );

where should i put these code in ?

Same question, where are we supposed to put this file ??