Photoshop: Ability to edit existing brushes in a set

Why can't the user edit brushes already existing in a set? I have a set I've been using for years and wish I could change the brush settings individually without having to recreate the entire set. Am I missing something here? As I understand it, once you've made and pasted a new brush in a set, you can't tweak a settting without creating a new brush, deleting the old one and moving the new one in its place. I'd be glad to be proven wrong and show me how.