I accidentally dismounted the Rendering Gallery from the bottom of the screen, and now it is obtrusively large.
Re-snapping it to the bottom doesn’t make it small again, and no re-sizing arrows pop up when mousing over the corners of the box.
I believe the issue of the largeness and not resizing when re-snapped to the edge of the screen is a bug.
The issue of not being able to resize the window in general is a usability problem, as screen real estate is at a premium in the rendering environment.
