The original idea by Johan Perjus, from https://medium.com/design-bootcamp/things-i-wish-adobe-would-address-with-adobe-illustrator-4796a89e1bae

When you create a new document, under More Settings you can indicate how you want the succeeding Artboards to appear (see the image).

However, if you add more artboards to the same document after it was created, this setting is not honored, but appears with the default setting, which is to the right of current Artboard. Even when the down and left icons are selected under Properties > Artboards > Quick Actions > Rearrange All Artboards.

On the positive side, Illustrator does appear to at least honor the Spacing setting (thanks to this now fixed report: http://illustrator.uservoice.com/forums/333657/suggestions/31986955)