Jon,
They already have the ability to do that. If you want to give the reason (and many times it is important), you would right-click and select inactivate. That puts the box right next to your pointer.
If you don't want to have the box pop up, you click on the Inactivate button at the bottom right. Perfect solution.
Unfortunately, although this is a great idea that would help the program tremendously and everyone would benefit from it, it will end up on the cutting floor because only three people indicated they like it.
