You were correct about how to finish the capture, but after the capture was made, a thumbnail was presented in the bottom right of the main screen. After I clicked upon that thumbnail, that's when the image went in front of everything and wouldn't move.
Eventually I noticed that I was in an image editor, and at the top left-hand corner there was a tiny circle, which started the process of closing that window, and asked a few questions. It was disappointing that this particular app didn't present the usual red, orange and green circle buttons.
The thing that made this even more frustrating was that when I used the Mission Control feature on the F3 key, that this editor wasn't in its own window, it was glued to the front of the Safari Browser and wouldn't separate from it, so clicking upon that panel, just brought me back to the same point.
But like I said, I was able to close the image editor and now all is well.
Thanks for your quick response, though.
On another note, it was really wild setting up the MacBook to be accessible with Google Chrome Remote Desktop, but after installing Rosetta, all was well.