code: def save_config(self):
          
          self.set_option('recent_projects', self.recent_projects)
          self.set_option('expanded_state',
                          self.explorer.treewidget.get_expanded_state())
          self.set_option('scrollbar_position',
                          self.explorer.treewidget.get_scrollbar_position())
          if self.current_active_project and self.dockwidget:
              self.set_option('visible_if_project_open',
                              self.dockwidget.isVisible())
docs: Save configuration: opened projects & tree widget state.
  
          Also save whether dock widget is visible if a project is open.