Editor Window

QT editors cannot be used during play mode. In play mode (or at runtime), QT uses a fundamentally different database that is geared more towards runtime-only functionality.

Dialogue Tree Editor

Dialogue can be created with the Dialogue Tree editor window. You can access it from Window > Quest Tree > Dialogue Tree Editor.

While the Quest Tree window is autosaved, Dialogue Tree isn't. Make sure to save any changes before exiting.