I want to implement alignment and layout functions, such as vertical left alignment of selected nodes
It would help if you provided small before-and-after screenshots showing the behavior that you want.
Have you seen the DrawCommandHandler extension? DrawCommandHandler | GoJS API
If that doesn’t have exactly the command you want, you can implement your own command.
That’s what the DrawCommandHandler | GoJS API command does if the user selects those three Parts.
See this sample: Drawing Commands
got it,thank you