You could set up Tool Presets that can be selected via Actions and those in turn by Function Key, but those would include the other settings, too.
Don’t know if a Scripting solution might be possible.
It looks like if I did this I would have to have an F key to tuen it on and then another f key to turn it off.
Scripting is best I think as I would be able to assign any key as opposed to F keys
Thanks just posted on PS-scripts in the hope I get an answer too