You may know that I'm a great fan of working on hard copy; it means you can get away from the computer; with biro on print the original and the amendments go on looking separate and you can see your changes of mind and second thoughts; and you're less likely to get lured into endless, muddly fiddling. Besides, brains are analogue and so is handwriting: and the former can control the latter much more intimately and directly than any process that has to go through a digitising interface, such as letters typed by your digits on a keyboard to appear on screen
So, call me stupid, but it's only now, something like six years after I first encountered Track Changes (as I remember, when the US copy-edit of The Mathematics of Love came through), and three after I started having to use them (grumpily) to mark my Open University students' assignments, that I've suddenly realised its potential for certain, particular stages in my own writing.
If you don't know what I'm on about, have a dig in your word-processing programme. Track Changes, essentially, shows everything you've done, without getting rid of what was there before. In MS Word I have it set so new text shows in red, and deletions are moved to comment balloons at the side; you can also have the deletions a different colour, staying inline but crossed through, and all sorts of other options and colours, to suit how you work. It's the electronic equivalent of still being able to see the original text on paper, no matter what biro marks you've made on top. When you've done everything you think this job needs, you just go through, review what you've done, and right-click each change (or group of changes) to either accept or reject it. What this means, of course, is that you can do all sorts of things that seem like a good idea in the depths of Chapter Five, and they're wholly and precisely reversible if you get to Chapter Sixteen and change your mind.
For example, I've just done some revisions to the WIP which entailed five big new scenes (for which I turned TC off), but also innumerable small changes all the way through what is quite a long and structurally complex novel. And having worked forwards and fast all the way through, I then went back to the beginning and could review what I'd done in the light of my overall picture of the revised novel, and accept it, adapt it, or ignore it. I then did a second pass, looking purely for cuts and, again, I could work forwards and fast (so holding the big picture in my head), and cut everything which seemed surplus, but without losing anything permanently, until I'd made sure that all I'd knitted up the holes properly; only then did I choose to make the cut stuff vanish for good.
If your revisions are very thick and radical - as they might be with your first pass through the raw, crazy first draft - it gets a bit tricky to read the whole thing fluently when you need to, so you'd probably be better off making a new version of the file and then working on screen. But it's perfect for those later stages, when the body of the novel is there and, now that you know what it is, you're re-considering and re-visioning everything. Some tiny changes are self-contained but some have relationships and repercussions elsewhere, and that's where having a record of exactly what you think needs doing, without doing it irreversibly, is amazingly helpful. Track Changes has gone straight (albeit belatedly) into my Process toolkit.