is there a quick way anyone knows of finding which keys are not assigned as keyboard shortcuts?
For instance I haven’t even mapped the flip tool yet because I always seem to think of mapping it when I am busy; then I try a bunch of keys and find they are mapped to other tools that I only remember when I use them 
I don’t know of a way to identify which shortcuts haven’t been assigned but you can get a list of the shortcuts that have been assigned via the Sketchucation Extension Store tool.
If you try to add a shortcut that is already taken, the dialog gives you a warning.
That’s a cool one, thanks @DaveR !
for even more joy its possible to easily remap your keyboard with powertoys
