Yes, I did as you said:

- I make 3 additional directories in my current project location: Animal, Animal/Dog, Animal/Cat
- [File] > [New file or project...] > C++ > C++ class
- Add Cat class in Animal/Cat; Dog class in Animal/Dog.

I expect that the Project tree would have Animal node, with 2 subnodes Dog, Cat. Each of them has 2 subnodes: Headers, Sources
But Qt Creator doesn't support, or I did something wrong: Animal node, with 2 subnodes: Headers, Sources. Each of them has 2 subnodes: Dog, Cat. I don't like this.

It'd be clear if you take several minutes to try it yourself

Thanks for your reply!