In order to fade in or out from a cutscene, a FadeTrack has to be created. Press the “+” button and select HorrorEngine→Fade Track

A FadeClip can be added to the track by right clicking and selecting “Add Fade In Clip” or “Add Fade Out Clip”

Adjust the length of the clip to determine the duration of the fade.
In order to show a letterbox during a cutscene (cinematic black bars at the top/bottom of the screen), a LetterBox Track has to be created. Press the “+” button and select HorrorEngine→Letter Box Track

A LetterBoxSetVisibleClip can be added to the track by right clicking and selecting “Add Letter Box Set Visible Clip”

Adjust the length of the clip to determine the duration of the letterbox and tick/untick the visibility on the clip inspector.

Unity timeline might skip your clips if they’re too short or if there is a framedrop. If you need to do an immediate fade or letter box at a specific frame, you can use the Signals available for this.
First, make sure your timeline has a Signal track with a CutsceneUtils assigned.

Next, use one of the following signals to perform these as an immediate effect