I have this dialogue topic that I want the player to answer "yes" or "no" and then never be able to see the topic again. I know how to do the yes or no, but how do I do the other part?

Have a look at Caius Cosades dialogue in the CS - he has a topic for each of the Blades reporting to him if we look at the one for Elone notice that one of the conditions is Journal - blades_elone2 - < 1 and in the results it says Journal blades_elone2 1 so what happens is the topic will dissapear after you have chosen it becuase the condition can now never be met as your journal now is set to 1 whereas before it was less than 1

I think this is the only place in game that the dialogue does this and it is a nice little trick to get rid of topic clutter