If you have two perpendicular sketches and are viewing or working on one sketch straight on; the dimensions of the perpendicular sketch should automatically disappear. See the image below, it's not as if you can read the dimensions. It just shows a jumbled mess, especially on complicated sketches. As soon as you rotate your view all the dimensions should automatically reappear. This should be an option you could turn on or off depending on your preference. BTW, I know you can turn off the dimensions of a sketch but that's a tedious process and doesn't happen on the fly as I'm suggesting. Thanks.