code: def remove_all_thumbnails(self):
          
          for thumbnail in self._thumbnails:
              self.layout().removeWidget(thumbnail)
              thumbnail.sig_canvas_clicked.disconnect()
              thumbnail.sig_remove_figure.disconnect()
              thumbnail.sig_save_figure.disconnect()
              thumbnail.deleteLater()
          self._thumbnails = []
          self.current_thumbnail = None
          self.figure_viewer.figcanvas.clear_canvas()
docs: Remove all thumbnails.