How can I find which Control-Command keys are mapped to particular programs?
There are a few apps out there which are meant to help show the available keyboard commands. The only ones I can remember right now are:
KeyCue which is €19.99 but does have a trial. I suspect this is probably the best of the bunch, although it’s the most expensive.
CheatSheet is another one, which is free, although it doesn't show nearly as many shortcuts as KeyCue does.
(If I can remember others I will edit this to add them)
Unfortunately, when I tried KeyCue and CheatSheet, neither of them showed anything for ⌃⌘D or ⌃⌘B.
I know that ⌃⌘Dis used for the system dictionary (highlight a word, press ⌃⌘D and you’ll get a dictionary lookup for it). But I don’t see a preference for it in System Preferences to allow you to disable it or re-assign it.
Also ⌃⌘B doesn’t seem to do anything on my Mac, so that may be specific to some app that you have installed.
Be sure to check the ”Services” area of Keyboard preferences:
That’s where I usually find the culprit when something has stolen a keyboard shortcut that I want to use.