Add this code to the theme’s function.php file to show some custom HTML when a user is not logged in.
add_action('my_wishlist_user_not_logged', 'my_wishlist_user_not_logged_20201908', 5);
function my_wishlist_user_not_logged_20201908($atts){
//echo '<pre>'.var_export($args, true).'</pre>';
?>
<span>Custom HTML here</span>
<?php
}

