When I launch Create Slideshow with photos in the Editor Photo Bin, the slideshow tool gets launched but it immediately goes into preview mode without any chance to do anything else. At no point can I do anything but save the slideshow to Organizer. I cannot export and change the Theme or Music or see the original photos.
The preview is created by design. And I agree that it is unfortunate that you can't cancel out of it until it is completed. But are you saying that you cannot see the other controls that are available? This usually happens if you have dual graphics processors on your computer. Here is what you should be able to see:
The Media icon. This allows you to add or delete or rearrange the photos and videos in your slideshow
The Themes icon. You can change the themes here.
The Audio icon. You can, change, add or remove your audio/music here.
In the Media tab, use this button to add or remove photos and videos.
The button to add or edit the Title slides.
If you cannot see these menu items, and you have two GPUs, you need to disable one of them.