Keyboard shortcut for clearing flag in Outlook
Solution 1:
In Outlook 2016 you can use Alt + Insert to clear the flag on a message.
Solution 2:
I found an easy solution : add a quick access button calling the built in function 'Clear flag' --> so I can access it with only one shortcut (ALT+4 in my case but it depends on the position of your button in the quick access toolbar).
Anyone with a better solution ?