The gallery in Publish shows the photos in your post's source folder. You can change the size of the thumbnails, sort and filter the photos, and choose which ones show.
How do I change the size of the gallery thumbnails?
To make the gallery thumbnails bigger or smaller, drag the slider at the bottom of the gallery.
How do I sort and filter the gallery?
To sort or filter the Publish gallery, click the filter button at the bottom of the gallery. From there you can:
Sort by Title, Creation Date or Modification Date, in Ascending or Descending order. The gallery is sorted by title, in ascending order, until you change it.
Filter by Stars or Colours to only show photos with a certain star rating or color label.
Click Clear Filters to show all your photos again.
What other gallery options are there?
The filter button also has these gallery options:
Split Used Images moves the photos already in your post to the bottom of the gallery, so it's easier to see which photos you have left.
Show Hidden Images shows the photos you've hidden at the bottom of the gallery.
Auto Add New Images adds new photos to the bottom of your post as soon as they're added to your source folder. See Automatically add new photos to your Publish post.
How do I hide a photo from the gallery?
To hide a photo you don't want to use, right-click it in the gallery and click Hide. Hiding a photo doesn't delete it from your source folder.
To see your hidden photos again, click the filter button and turn on Show Hidden Images. To bring one back, right-click it and click Unhide.