Can I prevent an app from overriding a system default keyboard shortcut? Sometimes I find that an app has it's own keyboard shortcut which overrides a MacOS default shortcut.

For example Airmail assigns ⌘← to hiding your message panel, I would much rather have this shortcut remain as the MacOS default (which moves your cursor to the start of the line). All the other shortcuts are fine, I'd just want to disable this one.

Is there a way to turn off a specific app shortcut so it reverts to the MacOS standard action?
If the app has a menu entry for the command, yes.

System Prefs > Keyboard > Shortcuts > App Shortcuts

Add an entry for your app &amp; the menu command you want rid of.
Set the shortcut to be something useless &amp; hard to hit by mistake...
This will give you your system shortcut back.

Example from another answer of mine, showing how to remove 'Hide Finder' - https://apple.stackexchange.com/a/177138/85275