Hi David,
Currently in order to add more images to a previously saved collage, you need to Undo until you’re put back in “Collage mode”. You’ll know you’re back in this mode when the collage layouts appear to the left (along with the rest of the collage controls such as Spacing).
In the future we will be looking at allowing you to edit collages without having to undo back into Collage mode.
Let us know if you have any further questions or suggestions!
