I had this idea that maybe they could just add a digital readout to the filter(s). The idea is something really small, that goes from 0 to 99. So when the filter is completely open, you'd get a reading of 0, and a reading of 99 for the other extreme. This would give 100 different options for/over the range of the filter, and would make it really easy to note/duplicate specific sounds.
Of course, another option one could always do if one wanted -which would be relatively easy- would be to design (probably with a computer) a little paper circle with lots of points on it that one could just put under the filter knob. Something that barely shows, but that you could line up the white line on the filter knob with to use as a reference. Maybe make a little paper circle with the 26 letters of the alphabet, pop off the filter knobs, install it under the filters and tape it (with a mild adhesive that wouldn't damage the finish) so it won't move.
Of course, another idea (that would of course be a bit more expensive) would be to have small little dots (like the side position markers) inlaid around the filter knobs. Having say 12 little dots around the filter (like a clock) would be very helpful at noting duplicating filter settings. You could maybe have 6 be blue and 6 be yellow (alternating) or some such thing.
Again, this is something that would be relatively easy for one to do ones self, by making little circles or something with colored tape and just putting it on.