https://gojs.net/latest/samples/treeMapper.html

I try to add a palette to drag and drop a node between two link items.

But when i drop a node from the palette i can't draw an arrow from it.

myPalette =
      $(go.Palette, "myPaletteDiv",
        {        
        "linkingTool.archetypeLinkData": { category: "Mapping" },
            "linkingTool.linkValidation": checkLink,
            "relinkingTool.linkValidation": checkLink,
            "undoManager.isEnabled": true,
            "ModelChanged": function(e) {
              if (e.isTransactionFinished) {  // show the model data in the page's TextArea
                document.getElementById("mySavedModel").textContent = e.model.toJson();
              }
            },
          nodeTemplateMap: myDiagram.nodeTemplateMap,  // share the templates used by myDiagram
          model: new go.GraphLinksModel([  // specify the contents of the Palette
            { key: "Alpha",  groupe : -3, color : "blue", text : "Concat" },
            { key: "Alpha",  groupe : -3,  color : "blue", text : "Concat" }
          ]),
          linkTemplateMap : myDiagram.linkTemplateMap,
          groupTemplate : myDiagram.groupTemplate
        });

I tried to add something like that but i don't really know what i'm doing.

Thanks for your answer