code: def _time_marker_move(self, event):
          
          limit = self.pixel_width
          x = self._canvas_ticks.canvasx(event.x)
          x = min(max(x, 0), limit)
          _, y = self._canvas_ticks.coords(self._time_marker_image)
          self._canvas_ticks.coords(self._time_marker_image, x, y)
          self._timeline.coords(self._time_marker_line, x, 0, x, self._timeline.winfo_height())
          self._time_show()
docs: Callback for <B1-Motion> Event: Move the selected marker