Currently, as far as I can tell, you can only watch replays at .5x, 1x, and 2x speed, but to view a previous part of the replay you have to restart the replay from the beginning. I think it'd be pretty useful to be able to pause and rewind a replay so that it is easier to see mistakes and whatnot. This would be especially useful on maps that aren't just a few minutes long. I looked for a similar request, so sorry if this is a repeat.