Add Customer Notes column back to orders page.

functions.php

<?php

add_filter( 'manage_shop_order_posts_columns', 'wc_define_columns', 15 );
function wc_define_columns( $columns ) {
	$columns['customer_notes'] = __( 'Customer Notes', 'woocommerce' );
	return $columns;
}

add_action( 'manage_shop_order_posts_custom_column', 'wc_render_customer_notes_column', 10, 2 );
function wc_render_customer_notes_column( $column, $post_id ) {
	if ( 'customer_notes' !== $column ) {
		return;
	}

	$order = wc_get_order( $post_id );

	if ( $order && $order->get_customer_note() ) {
		echo '<span class="note-on tips" data-tip="' . wc_sanitize_tooltip( $order->get_customer_note() ) . '">' . __( 'Yes', 'woocommerce' ) . '</span>';
	} else {
		echo '<span class="na">&ndash;</span>';
	}
}