When more than a screen-width of editor tabs are open, and one tab is "touching" the Show Window List (SWL) button, the SWL button functions as a context menu (as if the tab the button is touching, was right-clicked).
WORKAROUND
Close any tabs, that are no longer required, so that the last tab is not near the SWL button
STATUS
Issue is fixed in version 4.0. The latest release can be downloaded here.
