Re: Back up question amid heartbreak
My workflow is obviously different to yours. The way I do parts is to hide the staves that aren't relevant to the part I want to save, then print that part to a PDF, I do NOT create a separate NWC file for each part.
The staff belonging to the part to be printed is always the TOP staff in the case where there may be related/layered staves. This way any page system or page breaks can be made to the staff and will only be in effect when that parts staff is at the top.
When working on the whole work I have a top staff on which everything is hidden and it is layered with the next staff. This way system and page breaks relevant to the conductors/full score can be made and they do not affect parts prints.