Just wanted to share the obvious!
There is an excellent Manual for Devonthink on this site. I did download it a year ago and read it a few times.
Realized that it actually is updated when new versions arrive and it also has a lot of great links.
A great rediscovery - now I understand things I did´t a year ago when I bought the app. Never liked Manuals but this one is actually very good - recommended!