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.