Well hold W down and LMB now you get a markingmenu that has the option. It serves for this exact purpose but is way faster. If any of the options you wish to see aren't there change the marking menu.
But yes doing what you want is not terribly hard just put:
toggleUIComponentVisibility "Tool Settings";
in your keydown and keyup of a shortcut, or if your settings are separate windows then:
if (!`window -ex toolProperties`){
toolPropertyWindow;
} else {
deleteUI toolProperties;
}
Tough it works badly as the panel steals focus.