This system is used to save the info of the dialogs, so if a player talks with an NPC with different dialogs, this system will save the current element to play once the player returns to play.
For this, go to the upper toolbar of unity, select Game Kit Controller->Main Managers->Add Main Dialog Manager.
Then, this system is placed on the level, which is the Dialog Manager, and it contains the dialog prefab which can be placed in the level at any moment on any NPC, so the player can talk with them.
The process to configure is like the previous mission manager. First, configure the dialogs that you need (you can check the video tutorial for dialogs).
Once you have that ready, go to the main dialog manager, configure the Scene for the current level and press the button Get All Dialog Content Systems On Level And Assign Info.
Like that, all dialogs configured will appear on the list. And also, each dialog will receive the info of the Scene configured.