I run into the situation all the time when I have my laptop on my desk, the screen locks due to inactivity, and then I get called to run off to fix something somewhere. It would be nice to just hit the power button to suspend and go, but from the lock screen, the power button does nothing. I have to log back in, then suspend, and then I can go.

I know the power button is a per user setting, but is there a way to make the power button = suspend shortcut a system level shortcut?

according to this reddit post from martin (a kde dev), this is currently not possible. However, there does seem to exist a global shortcut whitelist!

btw, closing the lid on the lockscreen does suspend the system in my case!