If you cannot find the Lemur Editor window, perhaps after minimizing the application or using several monitors, you can try trashing the plist files to reset Lemur Editor to its default layout. You can also try disconnecting the extra monitors and using a single display. This applies to OS X only.
On the latest versions of OS X, the user Library folder is hidden. To access it, click on Go in the Finder's menubar while holding the alt key. The Library will appear in the drop-down-menu.