Would be great if we could click-and-drag the preview to pan it.
Currently the selection tool is activated on left-click/middle-click/right-click-and-drag, so I'd suggest activating the selection only on right-click-and-drag, and panning on left-click-and-drag.
The tiny panning square where the scrollbars meet is not enough. It's tiny, not accurate, and far away from the center on a large monitor.