Setting a multi-line `notesPlain` value on an edited item

I would assume that most of the metadata that can be added to a document should be preserved, but I don’t know which metadata isn’t currently preserved (I have not tested this in depth). The ones that I can think of immediately are tags and notes, and we know that the notes are not currently being preserved.

Out of a belt-and-suspenders approach, I am always specifying --filename and --title; ideally editing a document with a new file would keep the existing filename (that is, just replace the contents of the file) unless a different --filename and/or --title are provided.