Photoshop designed element to Qt

[wysota]

Can I continue using the Treeview and style it till it looks the same?

I don't think you can do that with just styling. But you can subclass QTreeView and provide your own painting and a custom delegate for items.

Or do i need other elements like a hierarchy of frames (which won't make the DEV team happy).

No, that's not a good idea.

An alternative is to use QtQuick where you can implement the whole tree in less than 5 minutes once you learn the technology.