I'm not quite sure what you mean. If you mean you don't want the trait or a trait description to show up in the character's list of traits, just use the Hidden attribute for the trait. Just search for "Hidden" in export_descr_character_traits.txt to see how it's used.

I always prefer to give traits description and effect text for debugging purposes. When I'm uncertain that a hidden trait has been acquired by a character, I can just comment out the "Hidden" attribute and reload the game.