Since this bug will never be fixed I offer a workaround for future reference for those who have the same problem.
Open KDE > Control Center > Desktop > Window-Specific Settings and use the "New..." button to add the slider, which is a window after all, to the exception list. There is a "Detect" button to identify the slider window, so keep the slider window popped up. Modify the Geometry > Position attribute to a fixed position on the screen. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]