How to disable middle mouse button to change to pan mode

GoJS
2

Presumably you have already set ToolManager.mouseWheelBehavior to `go.ToolManager.WheelZoom. In addition, you could override ToolManager.doActivate to force the wheel behavior to be zoom.

      $(go.Diagram, . . .,
          {
            . . .,
            "toolManager.mouseWheelBehavior": go.ToolManager.WheelZoom,
            "toolManager.doActivate": function() {
              this.mouseWheelBehavior = go.ToolManager.WheelZoom;
              go.ToolManager.prototype.doActivate.call(this);
            },
            . . .

[EDIT] Oh, I see you have discovered the same solution that I just rediscovered: How can I cancel the default middle click event?