There is a feature that I would like to see for the undo button: To make (part of) the undo history saveable. Sometimes I close anim8or, I reopen it, and I can't undo a small mistake I did before: major bummer. I will have to redesign the whole mesh. Well, you understand what I mean, part of the undo history to be saved in the .an8 file.
Well, this would make the .an8 files HUGE, but I have 2 solutions:
1) In the configuration, under the "undo buffer (MB)" setting, there can be an "undo history to be saved (MB)" setting, to specify the extra file size to be used in the undo history. (must be smaller than the undo buffer.)
2) There could be an "erase undo history from file" button in the file menu, to delete the undo history and to make the file smaller, if you are sure that it has no mistakes.