Can Timelines preview videos?

I am trying to mix different objects with a video and the amount of time wasted by going to Play mode again and again is just too much. I cant seem to find a way to preview the video in the timeline.

Is that impossible per design or am i missing something?

Thanks!

What do you mean by “mix different objects with a video”?

Just have them in the same scene, and combine the video playback (on a quad) with shaders, vfx ,etc. then have the camera projected on a screen.

In other words, using Unity to make audiovisual performances, not games.