You can drag-and-drop photos to any location. Simply click on the photo to select it, and then move your mouse cursor to the desired destination in a gallery.
You can also use CTRL + Click or SHIFT + Click to select contiguous or isolated groups of photos and move them to any location in a gallery.
The way you select photos on your computer is the same way you’ll select photos in your online folders.
Alternatively, If you want to make fast changes to your sort order, you can also sort photos automatically.