I hope I'm not embarrassed and the option already exists and I'm not aware of it. But I have two large screen monitors and usually use the darkroom skin in a darkened working environment. When working with 24 inch roll paper in QImage, the monitor screen is a blast of white light until the roll begins to fill up as the smaller print images are added. Or as each new page appears, the blast of white light happens. It may be helpful at times to have an option that the paper area appear as a fairly dark grey background rather pure white, with the grid lines simply a bit darker than the grey background.
Just a comment for consideration.

Mike, it's such a great software program, I'm amazed it does all that it does already and so well. The problem is, with everything else to concentrate on when your formatting the images, it is so easy to forget to turn it off before hitting the print button. I thought of it more as an permanent option like the skin colors. And when the paper is $4 a sheet this can be an expensive mistake. I still consider QImage a marvel at all it does. The new version 2023.100 is fantastic.