You can use custom tracking codes to run any script or plugin that you would normally run on your website.
You can use them to trigger facebook pixels, you can use them to show chat widgets or popups in your video, you can use them for almost anything.
Custom codes can be configured to run at a specific time or at the very start of the video. To configure a custom code simply select Add Custom Code
and in the settings you can configure when you want the code to trigger,