This problem is solved. I first corrected all outstanding syntax errors in the project. Then I right clicked on each user interface object in the screen, and in the black dialog that appears deleted all erroneous linkages to functions in the screen's controlling file that no longer exist. Each linkage has a little x icon in its upper right corner to do this with. There was also an out of date function name that happened because I had neglected to use refactor to rename it. So in the Assistant text edited (did NOT use the refactor function) to rename that function to the out of date name, and then used refactor to change that name to the currently intended name.

Never mind. I understand now. All the code inside the DispatchQueue's brackets is the thread, not the individual functions in it.

I found the answer: In the "Adjust Editor Options" menu (the 5 uneven horizontal line icon to the upper right, just to the left of the "Add Editor on Right" icon) uncheck the menu items: Layout Rectangles Bounds Rectangles

This problem is solved. I was using the wrong event. The event needs to be "Did End On Exit".

I solved this problem by manually creating the controlling file for the scene. It appears the creation of these is not automatic with the creation of a scene in the story board.

This problem is solved. I finally noticed I was getting the message that the application crashed because I did not have in my P-List the right key to give the user the reason why the app needs to access the Photo Library. I thought the key: "Privacy - Camera Usage Description" was sufficient. After adding also the keys: "Privacy - Photo Library Usage Description", and for good measure "Privacy - Photo Library Additions Usage Description", the app no longer crashed.