I googled "Cinema Director" with "Spine", and got nothing, so I've added some basic timeline support:

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For anyone not familiar, Cinema Director is probably the most popular cutscene/cinematic editor tool for Unity (citation needed). The main strength is being able to scrub backwards and forwards along the timeline, and arrange all your curves and cues without going into play mode. It's neat!

Out of the box Cinema Director supports Mecanim, but the downside of triggering Mecanim animations is that, on the timeline, it looks like this:

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That's a single marker triggering the beginning of the animation... but no visual info as to when the animation completes. Also Mecanim & Spine objects would not always play in the editor? And animations wouldn't start in a frame-perfect manner? Not sure what was going on, but not ideal. So decided to use SkeletonAnimation instead. Making the timeline action shorter in the editor alters the timescale of the animation.

Here's a Gist of the code for a timeline action.

(Doesn't support mixing or anything fancy, just plays animations.)