I use Paint.net a lot these days for sprite/pixel art, and I spend a lot of time zoomed in, offten on the edge of images, and I offten find myself having to move the tool boxes, or having to unmaximize the window so I can push them outside of the drawing canvas.
It occurred to me that it might be nice to by default, or by option, let the user scroll past the edge of the image by maybe 90% or 50% of the screen size so you can simply scroll a little further and not mess with the tool boxes.
Alternately maybe an option to contain the drawing canvas to an interior so it isn't under the boxes.
Just a feature I think would be nice. Keep up the good work