tl;dr: Third installment in a series highlighting lesser-known built-in Emacs features, requiring no packages and minimal learning curve. Highlights include `dictionary-tooltip-mode` for hover definitions, wildcard support in `find-file`/Dired, `compare-windows` as a lightweight diff, `kmacro-edit-lossage` for retroactively turning keystrokes into macros, `scroll-all-mode` for syncing window scrolls, `refill-mode` for actual auto-wrapping, and `emacs-lock-mode` to prevent buffer/Emacs termination. The author also shares Elisp snippets to extend `vc-diff` to work with backup files and improve other commands.