I used Notepad++ on Windows; now on MacOS I use TextMate. It's as simple and lightweight as Notepad++, and if I understand correctly, it has the save feature yo

I used Notepad++ on Windows; now on MacOS I use TextMate. It's as simple and lightweight as Notepad++, and if I understand correctly, it has the save feature you're looking for. If you Command+Q without saving to a file, the contents will still be there the next time you start it.