非主窗体在任务栏显示按钮

type
  TForm2 = class(TForm)
  private
    { Private declarations }
  public
    { Public declarations }
    procedure CreateParams(var Params:TCreateParams); override;
  end;

...

procedure TForm2.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  Params.WndParent := GetDesktopWindow;
end;