Dialogue System extends Behavior Tree to help create dialogues.
forum https://forums.unrealengine.com/showthread.php?88313-Dialogue-System
step-by-step tutorial https://www.youtube.com/playlist?list=PLUngfGDb9OrU1hbePrpxTg8suq_QSgQTH
To download Binaries go to www.mavrinsoft.com/dialogue