Monitors can be lost if dragged into the area of the config windows.

[RelentlesslyDIY]

If a monitor is dragged within the vertical bounds of the config windows, and released, it is not recoverable via mouse. Zooming the browser out to extremes can narrow the horizontal bounds enough to recover a monitor. Creating surrogate monitors, and switching them "up the order", can recover monitors faster than re-entering details.

A button in the config window to "reset position to center" or x=0 y=0 might be an easy solution, avoiding browser sizing issues.