possible to reduce size of Sigil window?

I've tried various search terms, to no avail. I'd like to "square up" the Sigil display on my monitor so that it shows up better in a screenshot. I was able to do this a few years ago in an earlier version (the Donate heart is shown, and of course there's no Preview Pane) but dang if I can do it now. Clicking the windows icon at top right of the screen changes the view only marginally. There seems to be no way of pulling the sides of the window toward the center of the screen, in either view. (I can pull it down from the top, so that it becomes shorter, and of course I can resize the Book Browser / Code View / and Preview Panel to occupy more or less of the available width.

Is this now impossible, or am I missing something obvious?

I'm using Windows 7 Professional edition.