I would like to be able to add a text field within sketches that doesn't serve any design purpose but simply communicates intention about certain dimension, or line, to fellow designers.
mockup
Such a text would ideally not show up unless one is in Sketch edit mode.
Haven't found a way to do this. I know about the normal Comments but they don't seem to reach within sketches. See Tag any type of object in Comments, especially in a sketch.