Which Diagram Layout to use?

Here you go, using your model data, plus a couple ImportNodes that I dropped into the Diagram and connected with Links:

This assumes that those blue ImportNodes are manually positioned.

<!DOCTYPE html>
<html>
<head>
  <title>Minimal GoJS Editor</title>
  <!-- Copyright 1998-2024 by Northwoods Software Corporation. -->
</head>
<body>
  <div style="width: 100%; display: flex; justify-content: space-between">
    <div style="display: flex; flex-direction: column; margin: 0 2px 0 0">
      <div id="myPaletteDiv" style="flex-grow: 1; width: 200px; background-color: floralwhite; border: solid 1px black"></div>
    </div>
    <div id="myDiagramDiv" style="flex-grow: 1; height: 400px; border: solid 1px black"></div>
  </div>
  <div>
    <button id="myLoadButton">Load</button>
    <button id="mySaveButton">Save</button>
  </div>
  <textarea id="mySavedModel" style="width:100%;height:200px">
{ "class": "go.GraphLinksModel",
  "nodeDataArray": [
  {
    "category": "DropDocletType",
    "key": "prepend",
    "id": "prepend",
    "text": "Prepend Doclet Type"
  },
  {
    "category": "DocletTypeNode",
    "state": "Diagram",
    "key": "1f409525-7df2-4bb6-b406-3e6be8e9b347-0",
    "id": "1f409525-7df2-4bb6-b406-3e6be8e9b347",
    "tags": "",
    "templateIndex": "-",
    "title": "Description of Work"
  },
  {
    "category": "DocletTypeNode",
    "state": "Diagram",
    "key": "1f409525-7df2-4bb6-b406-3e6be8e9b347-1",
    "id": "1f409525-7df2-4bb6-b406-3e6be8e9b347",
    "tags": "",
    "templateIndex": "-",
    "title": "Description of Work"
  },
  {
    "category": "DocletTypeNode",
    "state": "Diagram",
    "key": "2bb59c76-b54d-4b49-abbd-a0c6595d77bd-2",
    "id": "2bb59c76-b54d-4b49-abbd-a0c6595d77bd",
    "tags": "",
    "templateIndex": "-",
    "title": "Engagement Contacts"
  },
  {
    "category": "DocletTypeNode",
    "state": "Diagram",
    "key": "fc386d42-4874-4e3e-bb36-2e38430a17f8-3",
    "id": "fc386d42-4874-4e3e-bb36-2e38430a17f8",
    "tags": "",
    "templateIndex": "-",
    "title": "Communications Plan"
  },
  {
    "category": "DropDocletType",
    "key": "append",
    "id": "append",
    "text": "Append Doclet Type"
  }
],
"linkDataArray": [
  {
    "from": "prepend",
    "to": "1f409525-7df2-4bb6-b406-3e6be8e9b347-0"
  },
  {
    "from": "1f409525-7df2-4bb6-b406-3e6be8e9b347-0",
    "to": "1f409525-7df2-4bb6-b406-3e6be8e9b347-1"
  },
  {
    "from": "1f409525-7df2-4bb6-b406-3e6be8e9b347-1",
    "to": "2bb59c76-b54d-4b49-abbd-a0c6595d77bd-2"
  },
  {
    "from": "2bb59c76-b54d-4b49-abbd-a0c6595d77bd-2",
    "to": "fc386d42-4874-4e3e-bb36-2e38430a17f8-3"
  },
  {
    "from": "fc386d42-4874-4e3e-bb36-2e38430a17f8-3",
    "to": "append"
  }
]}
  </textarea>

  <script src="go.js"></script>
  <script id="code">
const $ = go.GraphObject.make;

// initialize main Diagram
const myDiagram =
  new go.Diagram("myDiagramDiv",
    {
      layout: $(go.TreeLayout, { angle: 90, layerSpacing: 20 }),
      "undoManager.isEnabled": true
    });

function nodeStyle() {
  return [
    { locationSpot: go.Spot.Center },
    new go.Binding("location", "location", go.Point.parse).makeTwoWay(go.Point.stringify)
  ];
}

myDiagram.nodeTemplate =
  $(go.Node, "Auto", nodeStyle(),
    $(go.Shape, "RoundedRectangle",
      { fill: "white", stroke: "royalblue", portId: "", toLinkable: true }),
    $(go.Panel, "Table",
      { margin: 5 },
      $(go.TextBlock,
        { font: "bold 10pt sans-serif", margin: new go.Margin(2, 2, 0, 2),
          minSize: new go.Size(16, 16), maxSize: new go.Size(160, NaN) },
        new go.Binding("text", "title")),
      $("Button",
        {
          column: 1,
          "ButtonBorder.figure": "Circle"
        },
        $(go.Shape, "XLine", { width: 8, height: 8 }))
    )
  );

myDiagram.nodeTemplateMap.add("DropDocletType",
  $(go.Node, "Auto", nodeStyle(),
    $(go.Shape, "Ellipse",
      { fill: "gold", strokeWidth: 0, portId: "", toLinkable: true }),
    $(go.TextBlock,
      { margin: new go.Margin(5, 5, 3, 5), font: "10pt sans-serif",
        minSize: new go.Size(16, 16), maxSize: new go.Size(120, NaN) },
      new go.Binding("text"))
  ));

myDiagram.nodeTemplateMap.add("ImportNode",
  $(go.Node, "Auto", nodeStyle(),
    { isLayoutPositioned: false },
    $(go.Shape, "RoundedRectangle",
      { fill: "royalblue", strokeWidth: 0, portId: "", fromLinkable: true, cursor: "pointer" }),
    $(go.TextBlock,
      { margin: new go.Margin(5, 5, 3, 5), font: "bold 10pt sans-serif", stroke: "white" },
      new go.Binding("text"))
  ));

myDiagram.linkTemplate =
  $(go.Link,
    { routing: go.Link.Orthogonal, corner: 10 },
    $(go.Shape, { strokeWidth: 2 }),
    $(go.Shape, { toArrow: "OpenTriangle", strokeWidth: 2 })
  );

// initialize Palette
const palMap = myDiagram.nodeTemplateMap.copy();
const importnode = palMap.get("ImportNode").copyTemplate();
importnode.isLayoutPositioned = true;
palMap.add("ImportNode", importnode);
myPalette =
  new go.Palette("myPaletteDiv",
    {
      layout: $(go.GridLayout, { wrappingColumn: 1, alignment: go.GridLayout.Location }),
      initialAutoScale: go.Diagram.UniformToFill,
      nodeTemplateMap: palMap,
      groupTemplate:
        $(go.Group,
          {
            locationSpot: go.Spot.Center,
            layout: $(go.GridLayout, { wrappingColumn: 1 })
          },
          $(go.Placeholder)
        ),
      model: new go.GraphLinksModel([
  {
    "key": 1,
    "text": "Import Nodes",
    isGroup: true,
    "category": "Imports",
  },
  {
    "key": 2,
    isGroup: true,
    "category": "PaletteDocletGroup",
  },
  {
    "category": "ImportNode",
    group: 1,
    isAssistant: true,
    "key": -1,
    "state": "Palette",
    "text": "PCD",
  },
  {
    "category": "ImportNode",
    isAssistant: true,
    group: 1,
    "key": -2,
    "state": "Palette",
    "text": "neo4j Query",
  },
  {
    "category": "ImportNode",
    isAssistant: true,
    group: 1,
    "key": -3,
    "state": "Palette",
    "text": "Python Script",
  },
  {
    "category": "ImportNode",
    isAssistant: true,
    group: 1,
    "key": -4,
    "state": "Palette",
    "text": "R Script",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "a34cc470-584f-491d-852c-e337b03ba9a9",
    "key": "b3dbd719-33f5-45bd-bba1-ad5cd152369f",
    "state": "Palette",
    "tags": "",
    "templateIndex": 0,
    "title": "Approach",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "94358ae0-c808-46f1-bee1-ceb18d65e387",
    "key": "9a444497-0183-4998-b790-011f65a8d8ae",
    "state": "Palette",
    "tags": "",
    "templateIndex": 1,
    "title": "Assumptions",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "eea7c2f2-a5c8-4e27-981e-b99add938e4f",
    "key": "407e8e11-dd29-474d-9bd3-81f61fc83334",
    "state": "Palette",
    "tags": "",
    "templateIndex": 2,
    "title": "Change Order Process",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "6feb527c-d956-46f5-8cc1-42261be3a0ff",
    "key": "91223f02-c8be-4cd4-a344-4e4bdee74f0c",
    "state": "Palette",
    "tags": "",
    "templateIndex": 3,
    "title": "Charges, Expenses and Invoicing",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "fc386d42-4874-4e3e-bb36-2e38430a17f8",
    "key": "adbee4fd-e067-42c1-887a-f60d0460a8d4",
    "state": "Palette",
    "tags": "",
    "templateIndex": 4,
    "title": "Communications Plan",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "c145e9fd-66c7-47d2-9cd9-b1aa5f0e9906",
    "key": "a495b561-c7a6-42ea-b4fc-92999bf3ba39",
    "state": "Palette",
    "tags": "",
    "templateIndex": 5,
    "title": "Deliverables",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "1f409525-7df2-4bb6-b406-3e6be8e9b347",
    "key": "34a15cc6-7e1a-40c1-9c41-791a6f9a71da",
    "state": "Palette",
    "tags": "",
    "templateIndex": 6,
    "title": "Description of Work",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "2bb59c76-b54d-4b49-abbd-a0c6595d77bd",
    "key": "9aa40170-bf05-4b5a-95e3-3d88b43f827e",
    "state": "Palette",
    "tags": "",
    "templateIndex": 7,
    "title": "Engagement Contacts",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "bc98aa1c-8a5a-444c-b41a-191cf5cfa261",
    "key": "1a9fe4a6-2ec3-4e82-9137-dc1ff4cad7d1",
    "state": "Palette",
    "tags": "",
    "templateIndex": 8,
    "title": "Escalation Process",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "46f32999-4fd4-46fd-a49b-d2ffb1e90533",
    "key": "c8523b52-07c2-4750-bf2e-821de65c8553",
    "state": "Palette",
    "tags": "",
    "templateIndex": 9,
    "title": "Initiation of Work",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "e34723c4-efd1-48e5-b134-c16475362833",
    "key": "ede62a24-3d17-49bd-aaf7-ab126e89a3cb",
    "state": "Palette",
    "tags": "",
    "templateIndex": 10,
    "title": "Introduction",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "6c12812b-5cf4-4e6f-bce2-16afccfb91c0",
    "key": "58be694e-7cf7-495f-88ee-412586e04ddd",
    "state": "Palette",
    "tags": "",
    "templateIndex": 11,
    "title": "IT&S Responsibilities",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "c4330a2c-d559-4800-8d41-b178e29ee1f3",
    "key": "1612b684-9cf8-4bb5-b308-3261edb82bb0",
    "state": "Palette",
    "tags": "",
    "templateIndex": 12,
    "title": "Kickoff Meeting",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "91177f3a-3c6d-40ea-bb76-7121fd6580f5",
    "key": "2603513c-02e2-40a7-a150-ef36b320cb8f",
    "state": "Palette",
    "tags": "",
    "templateIndex": 13,
    "title": "Project Dependencies",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "c42d5d77-4adc-40b4-a651-eb44d27958b4",
    "key": "5f7704ea-da1d-4989-969d-1e6581a460f0",
    "state": "Palette",
    "tags": "",
    "templateIndex": 14,
    "title": "Timeline",
  },
  {
    "category": "DocletTypeNode",
    group: 2,
    "id": "b8e39e14-24bc-4b87-af6a-845d56ebf405",
    "key": "a31e75d3-6a15-458c-aa27-443bf85b3119",
    "state": "Palette",
    "tags": "",
    "templateIndex": 15,
    "title": "TOC",
  },
])
    });

// save a model to and load a model from Json text, displayed below the Diagram
function save() {
  const str = myDiagram.model.toJson();
  document.getElementById("mySavedModel").value = str;
}
document.getElementById("mySaveButton").addEventListener("click", save);

function load() {
  const str = document.getElementById("mySavedModel").value;
  myDiagram.model = go.Model.fromJson(str);
}
document.getElementById("myLoadButton").addEventListener("click", load);

load();
  </script>
</body>
</html>