I would like to extend my Drupal 6 forum to easily see which questions have been resolved and which are still unresolved. I thought the best way would be to add a status field, but I can not find a way to add this.
What is the best way to easily mark forum topics in Drupal as resolved?
Try the Flag module. It will allow you to designate arbitrary "flags" to be associated with a post. It's super flexible.