Keyboard shortcut flashes my display If I press the keyboard shorcut  Cmd-Opt-Shft-Ctrl-W from any app it seems to flash my entire display.   I believe this started with Catalaina but I could be wrong.

I thought at first it was Keyboard Maestro doing it but the shortcut flashes my display even when Keyboard Maestro is not loaded.

Any ideas what  Cmd-Opt-Shft-Ctrl-W does and why it flashes the screen?
Quoting from this question: 

WifiDiagnostics files filling up drive even with logging disabled 


  ... that particular keyboard shortcut, command+option+control+shift+w, triggers something in OS X (possibly Catalina only; I don't have an older OS to test against) that starts the wifi logging.


So please check your /private/var/tmp.