Not to pressure but having open/save buttons (implementable either as upload/download Javascript shims) would be interesting. They can also be quine-like (I.e. you save the HTML and Javascript of the editor itself together with the content). I did once that for Suneditor but did not publish it, alas.
It's now a Gist because I only realised later that the original note will be deleted after 24 hours.
There are now two mechanisms that persist data between sessions:
1. Auto-saving to localStorage every 5000 ms (adjustable as per the instructions).
2. Manual data saving/download implemented using an anchor element that triggers a download. We can now restore markdown by loading a downloaded file (in principle this should work for any plain text file).
One important thing to note here is that localStorage doesn't work in private browsing mode and its behaviour is not entirely consistent between browsers. So I wouldn't rely too much on it!
Excellent. Useful for being on a chromebook, offline and not logged in, so only opening local html files for tools is an option (no Chrome extensions). Will add file saving to my copy.
Mn. :( By the time I found out about the 24-hour thing I couldn't edit my original post anymore, the Gist link that I included eventually include for an improved version was also a couple of levels down.