gtkmm & glade - multiple window not working

Question

using gtkmm.h header file, I created a simple app with glade template. Signal works fine but I am trying to change window or open another window on click event signal. member function fires but another window is not opening. If i create different Gtk::Application::create() then also 2nd window open after closing 1st one. Does anyone have any idea about this.? Anything can be helpful.

GLib-GIO-CRITICAL **: 19:45:21.107: g_application_parse_command_line: assertion '!application->priv->options_parsed' failed

and this is the error that shows in terminal.

event after creating different instances for Application and Builder below error shows up and 2nd window still fails.

Failed to register: An object is already exported for the interface org.gtk.Application at /org/gtk/Application/anonymous

Answer 1

Fixed by using childWindow->show();

but still there is one issue how to add widget like Gtk::Label into Gtk::Window or Gtk::Box when window is build using glade. I added by creating but shows no error nor label. I did something like below:-

Gtk::Label test;
test.set_label("Hello");
gtkBox->add(test);

Does anyone have any idea about this..?