Preview navigation
Viewport navigation changes how you look at the canvas, not the actual media transform.
Pan
Middle-mouse drag inside Preview pans the viewport.
Zoom
Hold Ctrl and use the mouse wheel over Preview to zoom around the pointer.
Reset
Ctrl+0 resets Preview zoom.
Detached Preview
Press F6 to toggle the detached Preview window. F5 controls the embedded Preview panel. The detached window is useful on a second monitor or when you want a larger viewing area.