Reorder WordPress post-list columns, adding a word-count column after the title column.

add-wordcount-column.php

<?php
/**
 * Reorder post-list columns, adding a word-count column after the title column. 
 *
 * This code assumes a new column named "wordcount" was already. 
 * Check the link for the whole process.
 *
 * @link https://imelgrat.me/wordpress/customize-wordpress-post-management-page/
 * 
 * @param array $defaults List of default post-list columns
 * 
 * @return array The list of original columns plus the wordcount column
 */

function add_wordcount_column($defaults)
{
	$new_columns = array(); // Create empty array to store new column order

	foreach ($defaults as $key => $value)
	{
		$new_columns[$key] = $value; // Add columns to new array
		if ($key == 'title')
		{ 
		    // when we find the title column
			$new_columns['wordcount'] = 'Word count'; // Add the word-count column after title column
		}                
	}

	return $new_columns;
}

add_filter('manage_posts_columns', 'add_wordcount_column'); // Register filter