This is a screenshot that exhibits the weird behavior of white rectangles appearing wherever I left-click a missing thumbnail that I have managed to make to reappear.
The thumbnails look as if all is well; however, if I attempt to select them for whatever reason, either they disappear again, or the white rectangles just sort of erase them.
Very curiously, I can press the Windows key and all the missing thumbnails will immediately appear — but I cannot do anything with them; likewise, when I attempt to take a screenshot, as soon as the screenshot selecting tool appears on the screen, all of the missing thumbnails immediately show up and thus I cannot capture the evidence of them being gone.
This screenshot also proves that I was not hallucinating when I said that, before the re-install, I was able to view two rather large thumbnails, instead of the three smallish one that are all I can manage now.
When I had uninstalled digiKam, I went back and installed the first version that I ever had and could not for the life of me manage to figure out how I managed to get the two larger thumbnails.
Although I do not have a screenshot, I could also choose to view a single very large thumbnail exactly as you see the two, except that it would be a single column of thumbnails, one per row.
Being able to do such allowed me to be much more accurate when adding tags, as I could better see the details.