After the recent Windows update, this Ctrl+Alt+Shift+F hotkey combination is reserved by Windows, I have even checked in safe mode where no other programs are running. I cannot register this combination in any program I use now. Besides, it's super annoying; I don't understand what it does and how I can change it.
This problem is reported on several support forums for products that use this key combination. According to all reports this is a problem introduced by the update to Windows 10 version 1903, when this key is swallowed up by Windows without doing anything.
It may be undone in a future update, or Microsoft will complete adding the handling of this new hotkey, but in the meantime here is what I found.
Using Spy++ I saw this funny sequence of events being reported for pressing these keys:
Ctrl down Shift down Alt down F up Alt up Ctrl up Shift up
Meaning that the event for "F down" was swallowed up by some component of Windows. If these three modifier keys are pressed then the result is that the F-key event is totally nullified.
I then tried AutoHotkey to intercept this key sequence, and this worked. Apparently, AutoHotkey hooks the keyboard at a lower level than whatever Windows component that swallows up the F-key, so is able to intercept and handle it first.
For associating this key-sequence with running Explorer, you could use this AutoHotkey script:
!^+F:: Run, explorer.exe
After installing AutoHotKey, put the above text in a
.ahk file and double-click
it to test. You may stop the script by right-click on the green
H icon in the
traybar and choosing Exit.
If you always want this script to execute, copy it to the user Startup folder at
C:\Users\<user name>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.