I'm coming late to this discussion. I'll start by saying that I'm an amateur, with relatively low volume, so these comments may or may not apply in your situation. I ingest (using II Pro) directly into my final file structure. Then when I import into Lightroom, I have it set the purple color label on all files. I don't use that color for anything else, and it gives me a visual indication of which images have not been worked on.
It sounds like you take one image and work it all the way through the process. I typically work on batches. For example, I found after returning from Cambodia with about 1500 images that the UTC zone was off by 2 hours and the time was off by 5 hours (I'm still trying to figure out how that happened!) It is easier to keep track of by doing the corrections all at once. Same thing for rating. Therefore I do one step at a time on all images in a batch. That means, though, that I often don't get to complete all the steps even within a working folder before I get interrupted (yeah, I know I'm the only one that happens to
. So I've found it useful in addition to the working folder approach to take Peter's list concept (Fig 7-14, p272), flip the rows and columns, and put it into an excel spreadsheet with the subtasks in each folder listed in the rows and a column header for the batch. That's about the only way that I can be absolutely sure what I've completed for each batch, especially as I tweak my workflow as I go along.
That said, I haven't given up yet on the idea of basing the workflow on labels/metadata as discussed earlier rather than on working folders, because this involves fewer file transfer and leaves things in a final location from the beginning. If I do that, your comment triggered a thought that color labels might be a useful part of that.