As you can see in the attached GIF, after a bit of scrolling in the images to be added, the screen will not close anymore. Only terminating the IDE will get rid of the screen.
It appears to be a more general problem. The introduction of TacShadowForm has broken popup windows all together. They won’t go away if clicking outside the window. They won’t go away after that, even if you click some close button inside the popup form. I presume that’s because they have become an image i.s.o. a real form.