O? The default is F5
However so far is impossible to add a shortcut to rotate the brush tip or a slider to the main window ( it’s only in the popup palette and i don’t use that).
You may want to check a plugin in this forum called SB alternate (switch brush) the author made it cause they wanted to change between different rotations of a brush but the way it works you can make any variations you want for a brush and cycle through them
Edit, found the link Switch to Alternate Version of Brush Plugin