Add a column to the WordPress posts overview/list.

add-view-post-overview-column.php

<?php
/**
 * add_view_post_overview_column.
 *
 * Add a column to the posts overview/list.
 *
 * @see https://since1979.dev/___/
 * @uses __() https://developer.wordpress.org/reference/functions/__/
 */
function add_view_post_overview_column($columns)
{
    $cols = array();
    foreach ($columns as $col_name => $col_data) {
        $cols[$col_name] = $col_data;
        if ($col_name === 'title') {
            $cols['viewpost'] = __('View post', 'namespace');
        }
    }
    return $cols;
}

/**
 * Hook: manage_posts_columns.
 *
 * @uses add_action() https://developer.wordpress.org/reference/functions/add_action/
 * @uses manage_posts_columns https://developer.wordpress.org/reference/hooks/manage_posts_columns/
 */
add_filter('manage_posts_columns', 'add_view_post_overview_column', 20);
?>