Problem: When making larger edits, and in particular writing new articles, there is a possibility of data loss (possibly a few hours worth) due to:
a power outage,
a browser crash,
a network outage (if one chooses to preview their changes while network is temporarily offline),
accidental browser closure.
It is a fairly standard feature in modern software to auto-save user edits to guard against such incidents. Auto-saving is ubiquitous in cloud-based software, where it has the added (or perhaps main) benefit of allowing the user not to think about saving their work/to carry on working on the same document in multiple sittings/across multiple devices. (This would arguably be desirable to have on Wiki in its own right.) "Offline" software also often has an auto-save feature, though generally for crash recovery only (e.g. LibreOffice).
The code editor does not currently provide any kind of auto-save functionality, while the Visual Editor appears to have some sort of auto-save implemented, or so I gather based on phab:T57370 (I do not normally use Visual Editor, so cannot tell whether it is indeed present; if it is, then it appears to be both undocumented and hidden, with no indication in the UI that anything is being saved - so almost as good as if it wasn't there at all).
Some workarounds that users, especially those who have experienced data loss in the past, are likely to employ include:
periodically copying their work from the Wiki editor to an external program (e.g. Notepad) and saving it locally;
writing whole articles in an external program and only copying them into a Wiki editor once ready;
writing their article in their sandbox and saving regularly.
Each of these is inconvenient/time-consuming/decreases productivity.
Proposed solution: A reliable auto-save functionality which regularly saves user edits in the background, which works both in the code editor and the Visual Editor, which allows these edits to be restored in the 4 cases listed above.
Desirable:
An indicator in the UI of the editor which tells the user if or when the page they are editing was last saved - to reassure them that auto-save is indeed present and functioning, and thus they do not need to resort to any of the workarounds mentioned above.
Saving these edits online (to Wiki servers), so as to allow the user to carry on working on one page in multiple sittings/across multiple devices. (Just to clarify: until published by the user, these edits should remain private and not visible to anyone else than the user in question).
Who would benefit: All editors, but in particular:
those who write larger articles, and two groups which, I believe, Wikimedia is particularly keen to recruit/retain:
new editors, who are likely to be particularly discouraged if their hard work is lost,
editors in countries, where power outages/"load shedding" occur frequently, which are disproportionally likely to be in the Global South (such as India or South Africa, if media reports are to be believed).
