Dans l'admin, étendre la recherche des Custom Post Type aux métas, en plus du titre et de la description.

admin-search-filter.php

<?php
/*
* Dans cet exemple mon Custom Post Type est "revendeurs"
*/
 
add_filter('posts_join', 'revendeurs_search_join' );
function revendeurs_search_join ($join){
    global $pagenow, $wpdb;
    // I want the filter only when performing a search on edit page of Custom Post Type named "revendeurs"
    if ( is_admin() && $pagenow=='edit.php' && $_GET['post_type']=='revendeurs' && $_GET['s'] != '')
	{    
        $join .='LEFT JOIN '.$wpdb->postmeta. ' ON '. $wpdb->posts . '.ID = ' . $wpdb->postmeta . '.post_id ';
    }
    return $join;
}
 
add_filter( 'posts_where', 'revendeurs_search_where' );
function revendeurs_search_where( $where ){
    global $pagenow, $wpdb;
    // I want the filter only when performing a search on edit page of Custom Post Type named "revendeurs"
    if ( is_admin() && $pagenow=='edit.php' && $_GET['post_type']=='revendeurs' && $_GET['s'] != '')
	{
        $where = preg_replace(
       "/\(\s*".$wpdb->posts.".post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
       "(".$wpdb->posts.".post_title LIKE $1) OR (".$wpdb->postmeta.".meta_value LIKE $1)", $where );
    }
    return $where;
}
 
add_filter( 'posts_distinct', 'revendeurs_search_distinct' );
function revendeurs_search_distinct( $where ){
    global $pagenow, $wpdb;
 
    if ( is_admin() && $pagenow=='edit.php' && $_GET['post_type']=='revendeurs' && $_GET['s'] != '')
	{
		return "DISTINCT";
    }
    return $where;
}

Oui