|Ice Porpoise Triptych|
You can use the same shortcuts in Photoshop Elements 10 and newer. To find the "Reveal All" command, choose Image > Resize > Reveal All.
And you can use these same steps to create a diptych (two images) or four or more images side by side.
I highly recommend all Julieanne's videos, which you can view by searching for "The Complete Picture" at Adobe.com.