Alright.. I'm sorry but there really isn't any more to this. Wherever you are in Sonar, 'q' always brings up the quantize window, as long as you have something that can be quantized selected.
...Well actually.. In your first post you say you press 'Q' in piano roll.. the shortcut you want to use is 'q' though. There is a difference between 'Q' and 'q' where the first one gives you the
input quantize window and the second one gives you the 'normal'
quantize window.
About the shortcuts in preferences: There's a search-box just above the list of functions in preferences-keyboard shortcuts. Type 'quantize' there and then just select the
area drop down box above that and use the arrow keys to toggle through that list. Wherever there's a function with the word quantize it will show up