Can I remove the lines in the Notes.app and change the line spacing?
I tried searching for keys for hidden preferences with strings /Applications/Notes.app/Contents/MacOS/Notes | grep, but didn't find anything.

There's no graphics for the grid lines, because they're just solid lines and their height depends on the font size. You can almost get rid of the grid lines by replacing paper.png with a solid color, but there's a light gradient drawn over it.



I also tried adding shortcuts for orderFrontSpacingPanel: and setLineHeightMultiplier: in DefaultKeyBinding.dict, but they didn't have any effect.