How to create photos using the app

When layering, I have found that tap and move done as separate movements doesn't work.  In order to drag up or down, you will need to tap and move in one movement.  That is, don't tap, let go and then drag.  Keep your finger on the thumbnail and drag.  

Also, if the thumbnail is already selected, you will need to select something else to unselect it before tapping and dragging.  

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I can't image that this was intentional.  It has to be a bug.  It may be fixed one day, or as with half of the bugs with the app, it may just be something you have to learn to live with.