Indicates whether the command can be assigned a binding to an external add-in. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 17.0.0.0 (17.0.1090.0) 
  Since:  2013 
  Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 17.0.0.0 (17.0.1090.0) 
  Since:  2013