How to display the context menu of a specific shape on left click?

I can assign a context menu to a specific part of a node by simply setting the contextMenu option, but I don’t see an option (for go.HTMLInfo) to set the default event to left click instead of right click.

Displaying the context menu when clicking anywhere on the node is easy though

myDiagram.addDiagramListener("ObjectSingleClicked", function(e) {
  var part = e.subject.part;
  if (!(part instanceof go.Link)) {
    myDiagram.toolManager.contextMenuTool.showContextMenu(myContextMenu, part);

But how can I detect which shape from inside the part the click event originated from?

From two days ago: How to open a context menu on left click?

Thanks a lot, I wasn’t able to find anything in google search whatsoever, should’ve tried to search this forum too.