dont know about shortcut but i know there is a prog which sits in system tray and all you do is click on it which brings up a menu then click on close all folders and that would close them all
I could find the url if no 1 comes up with anything...
iPhone X review
How to find a font: Discover the name of a typeface with these apps
The best iPhone for 2017
Les meilleurs logiciels de montage vidéo gratuits (en 2017)