What do you mean? It's in the trigger editor, after you made a trigger (it's in actions part as I've said), in part "Quest" (or it can be found in the full list).
If you do not know what each of the function does, here is a small description :
Quest Message - Displays a quest message to a player group and plays a sound (defined).
Create Quest - Creates a quest with a title, a message, and a icon.
Destroy Quest - Removes the desired quest from the game.
Enable/Disable Quest - Shows or hides a quest in the quest list.
Mark Quest as Completed - Gives the desired quest the tag "completed".
Mark Quest as Failed - Gives the desired quest the tag "failed".
Mark Quest as Discovered - Gives the desired quest the tag "discovered".
Change Quest Title - Changes the title for the desired quest.
Change Title Description - Changes the message for the desired quest.
Create Quest Requirement - Creates the requirements for the desired quest.
Mark Quest Requirement as Completed - Makes the desired quest's requirements completed.
Change Quest Requirement Description - Changes the desired quest's message's requirements.
Create Quest Defeat Condition - Creates a quest defeat condition.
Destroy Quest Defeat Condition - Removes a quest defeat condition
Change Quest Defeat Condition Description - Changes the message for the desired quest defeat description.
Flash Quest Dialog Button - Flashes the F9 button with stars until you click on it.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.