Working with layers in ArcMap to create graduated symbols allows you currently to use method = Manual with say 7 classes where you can Break Values at percents. Often doing this at percentiles like 30,60, 80, 90, 95, 97.5, 99.9 is helpful to find anamoulous populations. If you could edit a classification method, add more than 5 classes and SAVE the classification, allowing it to be recalled and used by others; that would be very helpful
