You can create new presets and give them name according to your choice but you cannot rename the default brush presets name.
To know the location, go to Lightroom Preferences > Presets > choose "Show Lightroom Presets folder" > open Lightroom folder > Local Adjustment Presets and that should contain all adjustment brush presets
Chetna - Thanks for your response. I was not trying to rename the default brushes, just some others that I had installed. One set of brushes had names starting with numbers (2.0.1, 2.0.2, etc.). I tried to make the naming of the brushes more consistent by renaming them in their folder, but they show up totally differently when I re-open Lightroom. As I said, I've done the same thing with Develop Presets, and it works perfectly. The only way that I've been able to change the name of a brush is by clicking the "Rename...." link in LR, but that's a slow process.
Thanks for the update.
That is the expected behavior. Adjustment brush presets can be renamed only via the renaming option in Adjustment brush panel itself.
They would not reflect the name changes according to renaming done in that presets folder.
Disappointing news, but thanks for confirming for me.