That section there is used to list the Objectives of the quest - for example, a quest to kill 10 Footmen and 3 Knights would list the first objective as Kill 10 Footmen and objective 2 as kill 3 Knights. Use the "Quest - Add Objective to Quest" function to add things to that part of the list. They're not entirely necessary but can make your map look more professional particularly if you later "tick off" the objectives for the player as they complete them.
As far as I understand, there's no real way to totally remove it.
For the purpose you're using it for, it could be a nice idea to put some info about the hero. For example, you could add a line for the Assassin in that section that says " - Good at surprise attacks and single target killing" and then maybe 2 or 3 more lines about the advantages of the hero.