So my quest for a (desktop) outliner continued after a night sleep. Now I'm done.
If you go to
Wikipedia >
marktaw.com >
Personal project planer you'll eventually end up at an open source application that I haven't been able to find mentioned anywhere else on the Internet.
The application is now called
Planz. There is a interesting video on the website.
It remains to be checked out. Hopefully, this is a what Tranglos is looking for.