I tried that option to get a scrolling window. And it did it.
From floating bar: I hit ctrl and rightclick to get menu, then Select Object, and the hit option 3 to Begin a Scrolling Window Capture on this Object - and yes it does scroll all way to bottom and produce a single image. The image shows several breaks all along it (like window captures, one after another). I prefer the image without showing bars or breaks. If I can only get this result, I can learn to live with it.