undoManager property
      
      UndoManager
      get
      undoManager
      
    
    
This read-only property returns the UndoManager for this Diagram, which actually belongs to the #model.
The default UndoManager has its UndoManager#isEnabled property set to false. If you want users to undo and redo, you should set that property to true once you have initialized the Diagram or its Model.
Note that the UndoManager might be shared with other Diagrams that are showing the same Model. The UndoManager might also be shared with other Models too.
Implementation
_i3.UndoManager get undoManager => _i4.getProperty(
      this,
      'undoManager',
    );
      
      set
      undoManager
      (UndoManager value) 
      
    
    
    
Implementation
set undoManager(_i3.UndoManager value) {
  _i4.setProperty(
    this,
    'undoManager',
    value,
  );
}