You either save an individual photo or all the photos of a given generation.
Save a single photo
When you are on a full screen photo view, tap on the bottom left icon as below:
Then tap on "Save Image" in the opening system share sheet.
ℹ️ If it doesn't appear at the top, scroll the list and you should find it somewhere below.
Save all the photos of a batch
To save all photos. tap on the top right button of the thumbnail view:
