calendar.on('beforeCreateSchedule', (event) => {
  const guide = event.guide;
  // Use guideEl$'s left, top to locate your schedule creation popup
  const guideEl$ = guide.guideElement ?
    guide.guideElement : guide.guideElements[Object.keys(guide.guideElements)[0]];

  // After that call this to hide the creation guide
  guide.clearGuideElement();
});