So when you do a line tool you can make it blurry, wide, etc. I think it could be handy to give it a option to half the line. im not describing it the best but essentually think if you are using a line to do some shading, it could cut the line in half, having a flush unblurred side on one side while the other would be blurred as per normal.

Attached is a very rudimentary example but gives the idea i was aiming at.