I was looking at my keyboard shortcuts (not that I can remember half of the ones that are assigned!), but looking at things I did more often and things I never used (and things I really didn't want to accidentally use, like toggling saving transparency assigned next to 'shift' to the / key..)..
But a one thing I did access frequently was blending options... so I figured, why not Ctl-Shft-B ? Little message pops up and says I can't use that key as a short cut. No reason given -- I tried just Ctl-B, but it was assigned to something else (color balance or such and gave an ominous "you can't use _any_other_ key for color balance"..(Huh?)...whatever..., went back to my 1st choice Ctl-Shft-B. "You can't use this key as a shortcut...Grrr...well, what happens if I just hit enter?...
Click -- it saved it. save config choices.. press Ctl-Shft-B -- Up comes Blending options. ?!?!!?
I'd never seen such a weird message --- several other combos use Ctl-Shft-<letter>, so why would it complain about C-S-'B' but weirder... when I just go ahead and 'do it., it works? Why would I be told I'm not allowed to use a key combo when I am? Is there some law I don't know about?
Just wondering what else I'm told I can't do that I really can and wondering what else is not really true when it gives prompts that seem entirely illogical ---- and that are also 'wrong'?
'Ctrl Shift B' is Auto Color. Watch your history palet as you try possibly available shortcuts, and see if they do anyting.
I don't understand where that message would come from. I only get "already in use and will be removed from xxx if accepted", and then I accept and everything's fine.
Incidentally, I have <shift+ctrl+B> assigned to Convert to Smart Object (no idea what it was originally), so it's not as if that particular shortcut is locked in any way.
What you cannot do is use single-letter (tool) shortcuts for menu items, but that's not the case here.