copy/pastefindershortcut
I made a shortcut with Automator to open a file with VS Code in Finder. But I can't assign it to the desired keyboard shortcut (command + option + c) because it is already taken by 'Copy "filename" as Pathname' shortcut. I can't reassign in System Preferences -> Keyboard -> Shortcuts -> App Shortcuts because it has a variable name in it.
Automator script to open VSCode
Go to System Preferences → Keyboard → Shortcuts → Spotlight and disable the Show Spotlight window option.
I think the OS X Human Interface Guidelines are the place you're looking for. They state that there are Apple-reserved shortcuts (e.g. cmd ⌘+space) and also “expected behaviours” (e.g. cmd ⌘+c) one should respect.
While they don't explicitly state the priority, it suggests itself that the System always should have priority before the frontmost (active) and then background applications.
From my experience, you’re on the safe side with multiple modifier keys (i.e. cmd ⌘+ctrl+shift+…).
As an aside: regarding your specific example (assigning a shortcut to open a new terminal) there's also excellent apps for that, TotalTerminal (Terminal.app extension) and iTerm 2 (Terminal.app replacement) come to mind
Best Answer
Here is how I used the control + command + c keys in Keyboard Maestro. It's a paid app with a free trial period. Frankly, I didn't have much luck defining apple's keyboard short cuts. It was all confusing to me.
Start up Keyboard Maestro https://www.keyboardmaestro.com/main/
Keyboard Maestro does come with an assist to help you create your first action. It's a little confusing at first to figure out what button to click when. They do have a forum.
click on the plus icon to create a new action
pick what key you want to be the hotkey. ( not shown )
add a new action. request to see the list of actions
create new action.
Pick your action.
Resulting page.