However my post isn't about that, even if I'd strongly recommend (IMHO) that the last button should be the "Close" and not the "Delete", especially because the 'Delete' icon button resembles sooooo much with the Close icon button present on all OSes.
My post is about Closing a view. We cannot (re)show it.
Example:
I have 4 photos to compare.
I choose 3 and I close one view in order to see a bigger area from the 3 which remained.
I finished my compare and I want, using the thumbnail strip to go and compare the next 4 photos.
Expected: Wheeeee!!! So easy and natural...
Actual: Boooo!!..... In order to see again 4 viewports I need to close and reopen the Compare Window.
Implementation proposal:
Add 4 (or 3?) buttons labeled 1,2,3,4 which when pressed will show the corresponding number of views. It doesn't really matter what photo the engine will put in the newly opened views. I'd suggest the next ones from the latest opened photo, but it doesn't really matter.
GUI proposal:
