Ok, but since Dr. Andus uses Windows and wants to CRIMP with Linux software I only considered outliners that run on Linux but not on Windows, which -- to my knowledge -- are none.

- Notecase Pro is multi-platform
- TuxCards looks the opposite of alive to me (last updated in 2010)
- Vimoutliner is a Vim package which I suggested in my reply
- Scrivener on Linux is dead as far as I know. It was a community port from the beginning and doesn't have official support.
- MindRaider doesn't look to active either. The repo moved to GitHub but there are open issues about broken exports from 3 years ago (opened by the author himself)

Franz Grieser wrote:

Jan S. wrote:
>To my knowledge there aren't any "Linux Outliners".

What about Notecase Pro, TuxCards, Vimoutliner, Scrivener, Mindraider,
Ultra_Outliner - just the first few a simple Google search brings up.
And they all seem to be alive.