I recommend to create regions which stand in context with the video information. That's quick and helps a lot to jump between scenes and motives.
Of course it would be very nice to have a thumbnail preview. But I don't need it badly. This requires zoomed tracks to recognize whats in the thumbnails, and before I have focused a tiny image in between others I already have jumped to the region and scrubbed to the place where I wanted to work on.
But anyway. This is standard in other video software and works with still images already. So ...
It also would help to isolate video from audio visually.