"If you want to use widget again, you need to add a reference to it while it’s  not inside a container, using g_object_ref()."
                                                                                
This is ambiguous. It suggests that a reference should be added after the widget has been removed from a container (while it's not inside a container). 
                                                                                
I suggest, "If you want to use widget again, you need to add a reference to it  before removing it from a container, using g_object_ref()."