Ah, thanks, that explains it.
I would appreciate it, but there is no rush, I can live without. I do think that "branch lines" should be default in the Model tree, without needing to set a stylesheet. It would help newcomers understand the tree structure better - and help experienced users too. But this seems to be controlled by the host system's default for file lists, and since Win7 and on Linux DEs too, lists no longer use branches as in the WinXP era. It may be OK for desktop file explorers, or a help file, but for a parametric CAD program's history tree, I think it's a usability setback.
FYI https://doc.qt.io/qt-5/qtwidgets-itemvi ... ample.html shows this image:
I'm afraid I have completely hijacked Kurt's topic.