The Magic Wand in Publish builds the layout of your post for you. Click it, and Publish adds photos from the gallery in a ready-made layout that you can change afterward.
What does the Magic Wand do?
When you click the Magic Wand, Publish adds photos from the gallery to the end of your post in a repeating pattern: one large photo, then two side by side underneath it.
Each click adds 9 photos until you change it. Click the Magic Wand again to keep adding more, until every photo in the gallery is in your post.
How do I change how many photos the Magic Wand adds?
To change how many photos the Magic Wand adds, click the drop-down next to it and choose 3, 6, 9, 12, 21, 42, 84 or All. Publish remembers your choice for next time.
In the same drop-down, you can choose how it picks photos:
Pick from first to last adds photos in the order they show in the gallery. This is the default.
Evenly distribute picks spreads its picks evenly across the whole gallery, instead of taking the next photos in a row.
How do I choose which photos the Magic Wand uses?
The Magic Wand uses photos in the order they show in the gallery, and skips photos that are already in your post or hidden. To choose which photos it uses, sort and filter the gallery first. See Filter and sort the Publish gallery.
For example, if you filter the gallery to only show 4-star photos and then click the Magic Wand, Publish builds your post from your 4-star photos.
To take back what the Magic Wand added, choose Edit → Undo.