Actually, perhaps I could leave the n-panel open with the brush settings visible - I'll try that next time
I'm not at home to test this, but have you tried right clicking on the option and seeing if it has the option to add to quick favorites? Then you can just press q to bring up quick favorites and change it there. I can check other options when I get home in about 5 hours.
Martin that sounds great I'll take a look this evening! And there unfortunately isn't Dwayne!
It's not what you want, but it might work for you. On the tool setting bar(The second line of the header) there is an offset dropdown button. You can right click on it and assign a hotkey. I used F5 since I know that F5-F8 are free. This brings the whole falloff section to the mouse cursor, but you can quickly see what it's set too and change it if you want then just move the mouse cursor out of the box and get back to work. The only other option I can see is to create an addon/extension that will do it.
Yeah, Dwayne suggestion of assigning a shortcut to the Falloff dropdown is probably the best you can get.
The problem with the Spherical/Projected Setting is, that it is per Brush. So you'd have to assign a shortcut for each Brush.
For an Addon, the Python would be, for the first Brush: bpy.data.brushes["SculptDraw"].falloff_shape
I figured out how to create the buttons based on the brush on the selected brush in the n-panel. I just don't know how to create the pop where the mouse is at. I can even assign a hotkey. One day I'm going to sit down and learn Python. Until then I'm limited on what I can do.