Choose Tools, External Tools, Batch make album. Now try to click the Cancel button. It doesn't react. Closing the window by hitting the "X" works.
ETA: I realize that the Cancel button is intended to cancel an active operation, but it's "live" even before you kick off the routine, and one's normal expectation is that it will close the window. I notice that the line to close the window is commented out in the code.
The Cancel button should be active only while the albums are being processed, and maybe relabeled Abort. There should be a Close button to cover the "normal" situation.