A quick Kagi found a few of them, apparently a Waffle House has to be a certain size, and if they can do more business, it spawns another one.

They're on Chamblee Tucker Road right off of I-85 in NE Atlanta. Here's a screenshot from Google Maps: https://ibb.co/0tdBRR1

Now that I think about it I actually used to drive past them sometimes! Only one of them shows up on Waffle House's own map, though.

Here's an article talking about double Waffle Houses, from 2019, when the older of the two at Buford Highway / I-285 closed: https://www.tonetoatl.com/2019/07/Waffle-House-Closed-Buford... - they mention the pair on Chamblee-Tucker. Apparently one is catering-only, which probably explains why it doesn't show on the map. They also mention pairs that used to exist at Clairmont Road near I-85 and Lawrenceville Highway near I-285. Apparently WH is trying to reduce the number of these.