All the mac keyboard short cuts like Cmd + Q (Quit Simulator app), Cmd + K (Toggle keyboard hide/show in Simulator) etc has stopped workings for iOS Simulator app since this morning suddenly.
All other apps, including Xcode, shows the shortcut in menus and they are working fine.
I noticed, the shortcut keys shows up against menu items momentarily on launch of simulator but then disappears completely (see attached)...
I tried following but no success...
Launch simulator (Open Xcode project and then menu Product > Run. And, directly through menu Xcode > Open Developer Tools).
Erase All Content and Settings in Simulator...
Restart Mac
Xcode 9.0.1 (9A1004) | Mac 10.13 (17A405)
You might have enabled (checked) the "Send all keyboard shortcuts to device" mode. It's in the Hardware > Keyboard submenu.
Pressing both Left and Right Cmd keys at the same time will exit keyboard capturing mode and re-enable menu shortcuts.