The Modern theme builds its archive index out of the same 600px reading column it uses for posts. That's the right width for reading an email, but on a wide desktop it left a tall single column of posts marooned in the middle of the screen with a few hundred pixels of empty space on either side.

You can now hand that space back to your posts. Head to your archive settings and you'll find a new Archive layout option on the Modern theme:

• Single column — exactly what you have today. This is the default, so nothing changes unless you ask it to.
• Two-column grid — on screens wider than about 900px, the index lays out as a two-column grid so more posts fit above the fold. On phones and narrow windows it stays a single column, so your mobile readers get the same experience either way.

It's purely a layout choice for the index page — your post pages, cards, and everything else look exactly as they did. If you've been wishing your archive felt a little less like an endless scroll, give the grid a try.

Two columns not enough? The Arbus theme goes all the way to an image-first grid if your newsletter leans visual.