I have copied my KM macros over to another machine. On the new machine, I notice that one of my app-specific hotkeys wasn't working ( control + 1 ). I cleared the keystroke to reenter but it was not accepting the combination.
My assumption is some other app -- outside of KM -- is already using that hotkey. I quit as many apps as I could but still no luck.
Is there a way to find out -- system-wide -- what app that hotkey is assigned to?
Keyboard Maestro will usually override system set hotkeys...however there can always be outliers. You can check in the keyboard / shortcuts pane of preferences to see what hotkeys are currently assigned. You can also look into apps that show you system-wide and app specific shortcuts such as KeyCue. It can present you with a window that shows you every currently available hotkey shortcut in a window like in the screenshot.