There are times, especially after following a rather complex set of operations to create an effect.. After doing and in many cases re-doing to get what you want, when you're finally satisfied, you save the image to not lose you're hard work, and then set off to do the next step on a new layer. (The preceeding paragraph is my third attempt, and is still very badly written. I can only hope the point is illustrated.)
Well, after saving.. to help clear up the History window, I usually have to close and re-open the image. It would be nice if somewhere on the History window there was a button (and possibly a corrosponding keyboard shortcut) to clear that history. What this does is make that history window much easier to manage. The steps you take from this point forward can be undone all the way if you like, but won't go back past the point where you cleared the history.
You can, if you so choose to. add a line when clearing called [History Cleared], which itself could be undone if one chooses to. This would have the effect of condensing all of the history up to that point into one line, so that finding that point would be as simple as scrolling to the top of the history window. But that's only an option if you feel it should be in there.
*note* it's early, and I have only been up for 30 minutes. This is why my post here is not very clear. I'll try to re-write it in a while to get my point across in a much more clear fashion.