When you hover over item from window list, window thumbnail appears. But when you left click item to open a window, after the window is open, the window thumbnail isn't closed. (please see attached screenshot).
It would be better if after opening the main window, window thumbnail will disappear, since after the main window is open, there is no sense of open window thumbnail.
I think it is generally unnecessary to show the preview if the window has focus.
It only shows as long as you hover the item in the window list. That is how it's supposed to work.
Even if you hover the item in the list, and the window has already had focus it is unnecessary to show the preview. It's just my opinion.
Most helpful comment
I think it is generally unnecessary to show the preview if the window has focus.