I don't know if this will be of help to anyone with RTK1 Ed. 6, but I made a Google Docs spreadsheet to compare the numbering of the new edition with older ones. (If you're using the 6th Ed. with this site, the spreadsheet should show when to add out-of-sequence kanji.)
Thank you Katsuo, that was exactly what I was searching for!
Now I've got to figure out an easy way to change my Anki deck and adjust the numbers.