In an urtext score, I am using grey+cue size to indicate passages that are e.g. col basso and not explicitly notated in the source. Just as it is possible to change the color of tied noteheads in Engrave mode, I wish it were possible to change the color of any notational feature in Engrave mode. For instance, in this screenshot, I would love to see the accidentals, stems, and beams in grey as well as the noteheads:
As an aside, It’s wonderful how the Set local properties feature allows this to be done locally without affecting readability in performance parts!