1. asciinema[0] has the ability to record a terminal (and thus, terminal-based editors) and replay it. By default, the replay comes with pause (via <SPACE>) and play-single-frame (via <.>).

2. Vim has Mundo[1] and Emacs has undo-tree[2] which allow you to step backwards-and-forwards through your changes.

As I see it, adding explicitly-selected frames to any of these features should be possible.

0: https://asciinema.org

1: https://simnalamburt.github.io/vim-mundo/

2: https://www.emacswiki.org/emacs/UndoTree