Here is the video:
This screen is the attached screen connected with DisplayPort to a MacBook Pro 13" early 2015,
defined as second screen in System Preferences > Display > Arrangment
When the mouse stops, I hit the combinaison of keys to show Alfred, but it shows on the main screen even if the active window is the fullscreen one under the mouse on second screen.
It happens with any application in fullscreen, here I tried with iTerm and iTunes
Most of the time, I use the keyboard to switch from one app to the other, so the mouse stays on main screen but active windows is o