Alert when unsaved sheet opened for longer than an hour

[AntonBogun]

Reading in discord I saw that despite autosaving every once in a while, if a file hasn't been saved then there will be no autosaving, therefore all progress will be lost in case of a crash. I would say there should be an option (on by default) to alert the user every hour or so (of active usage time) that they have a file open with no save location.

[aardappel]

That should hopefully not be a frequent occurrence.

Could pop up a save-as dialog after 5 mins, or even right at the start.

[s7726]

Could store and save all new files to a temp location prior to the first user initiated save.