Sorting photos by event instead of album

There are no Events in Photos.app. Your Events were converted to Albums in the new app. They're stuck in a Folder named 'iPhoto Events' but they are albums.

Albums and Folders work the same way as in iPhoto.

Albums can hold Photos

Folders cannot hold Photos. Folders can contain Albums or other folders, but you cannot drag a photo to a folder.

There are two ways to addd images to an Album: You can drag and drop - but it must be to an Album, not a Folder. Or, you can select the images you want to add to the Album and use the + button in the toolbar. This ll allow you to either create a new Album or add the pics to an existing Album.

To me, it makes sense because Event, which does not really exist on Photo anymore, is the source library.

And this part has been replaced by the automatic splitting into Moments, Collections, Years. Photos has only one big event.

Have you explored these automatically created subdivisions of the library? You can step between these views from the "Photos" view of the library, using the arrow keys to the right of the "traffic light" in the upper left corner of the window.

Moments in Photo are the new Events. There's a way to simulate events in Photos.

When the library was first migrated there was a folder created titled iPhoto Events and all migrated iPhoto Events are represented by an album in the folder. To open the sidebar if it's not open use the Option+Command+S key combination.

When new photos are imported into the Photos library go to the Last Import smart album, select all the photos and use the File ➙ New Album menu option or use the key combination Command+N. Name it as desired. It will appear just above the iPhoto Events folder where you can drag it into the iPhoto Events folder

When you click on the iPhoto Events folder you'll get a simulated iPhoto Events window.

The downside to the simulation is that the Album/Events can only be sorted automatically by Title. But they can be sorted manually.

Ask Apple for more sorting options in Photos via https://www.apple.com/feedback/photos.html.