I know what you mean about references being helpful for the writer. One of the things I find hardest to remember, in stories, is physical description. Yet that's something that many readers remember well; changing a character's eye color, once mentioned, is likely to bug a lot of readers. Consequently, I put physical appearance into this list, for me, to help me stay consistent.

Updating will therefore include adding new details as well as adding new people. Though I remain committed to not putting spoilers into supporting materials that I share with readers. (Information that the reader learns in the first scene where a character is introduced is generally not a "spoiler". Happily.)