I have found this in Lightroom Help:
When applying and working with multiple local adjustments, keep in mind the following:
My problem is this does not work as advertised. I'm experimenting on a photo and can make my A and B brushes. But I can only see the edit pin for A. The pin for B never shows up. Hitting H multiple times does nothing but toggle the visibility of pin A.
Nevermind I just discovered what it means to make a new brush. It is not A and B but there is another control called New just under the icons for photo adjustments. I'm not sure what the logic is behind having a A and B under one brush. They become two brushes controlled under one pin.