Ties into the default terminal plugin to save command history (press up to replay old commands) across reloads.
History will be saved to the plugin's folder (~/.octoprint/data/persist_terminal_command_history/command_history.json)
Install via the bundled Plugin Manager or manually using this URL:
https://github.com/nivekmai/OctoPrint-PersistTerminalCommandHistory/archive/master.zip