How do I set Actor To Track keyframes in Sequencer

I have a cinecamera on a rail and want to track different actors depending on the position on the rail. I set up the first actor I want to track, and clicked the keyframe icon next to the ‘Actor To Track’ property on the camera. This adds a ‘Actor To Track’ track in Sequencer to which I can add keyframes, but I can’t figure out how to change the tracked actor at any given keyframe.

Did you ever get an answer to this - I’ve just hit the same problem

Just figured it out. With the details panel for the camera open change the Actor to Track under look at tracking and then press the add new key button.