In versions of Outlook pre-2016, this functionality existed in the Move To: Quick Step. It was renamed Archive in Outlook 2016, and there's a larger button, but it's the same as the old Quick Step.
Right click Archive in the Quick Step pane (or Move To if
you're using an older version of Outlook
Click Edit Archive (or Edit Move To in older versions of Outlook)
Specify a Shortcut key combination from the drop-down
In Outlook 2016, if you hover over the Archive button, it tells you that Backspace is also a keyboard shortcut. I can't speak for other versions of Outlook.
