Alternative

I downloaded the plugin but did not install it when I saw the number of files.
It might be great, I won’t say anything on it, I just wanted to share a few lines of code that did the job for me instead:

if (defined('WP_DEBUG') and true === WP_DEBUG) {
  // add a green dot at the bottom left of the screen
  // when WP_DEBUG in wp-config is true
  function devTag () {
    echo '<div style="background:green;border-radius:10px;bottom:20px;height:10px;left:20px;position:fixed;width:10px;z-index: 9999;"></div>';
  }
  add_action('wp_body_open', 'devTag');
}