How to make multiple windows in an application?

Question

Qt Creator

How to make multiple windows in an application?
That is, there is a main window, it is necessary that by pressing a button or something else, another window opens, also with other widgets, including buttons, i.e. with which you can interact (the main window remains open). Zater closes this auxiliary window and continues working in the main

one. How to make this second window? I can display informational messages, but there is only a button template, you can’t add your own widgets
Preferably in qt designer, not with code

Answer 1

Making programs with gui in python is a bad idea
Switch to C# + WPF

Answer 2

MDI interface

Answer 3

https://stackoverflow.com/questions/36768033/pyqt-... , apparently this is needed.