Some hotkeys not working for certain apps I'm trying to understand why select hotkeys will not work in certain apps. For example, Command+ will not work in WhatsApp to make text bigger, and CommandControlF will not work in Joplin to make it full screen. 

My suspicion is that another application is hijacking this hotkey, but how do I verify this? How do I check which commands the computer is actually executing?
Nothing is being hijacked.  To make an app full screen or to make text larger, it must be supported by the application.  This holds true for not only shortcuts, but text substitution as well. 

A quick search of the Mac Keyboard Shortcuts for the Full Screen shortcut says this:


  Control-Command-F: Use the app in full screen, if supported by the app.