Quote Originally Posted by wysota View Post
If you ignore the parent, you will never receive a tree model. You also have to return indexes from the proxy model and not from the source model. The only method that can and has to return indexes from the proxy model is mapToSource().

I still fail to grasp what is the effect you want to obtain. Maybe a very simple practical example would clear things up?
Take a table with two columns and two rows and following data:
1,2
3,4

I want to be able to click on “1” so it expands to “2”,
I want to be able to click on “3” so it expands to “4”,

In other words as already stated: each record represents the path of a tree.