Hi! Just downloaded the new v9 
Looking at the new task system and want to try it out. Is there any information available how te set this up, like adding a new tasks? I’ve seen the video from last summer (Version 9 Sneak Peak: Automated Tasks).
I hope there will be some documentation about how to use it as a developer.
Yes, this is on our list of things to document, although it hasn’t been done just yet. I hope to have some of this documentation launched next week.
Heads up: new task documentation for editors is available here.
https://documentation.concretecms.org/user-guide/running-site/tasks
Developer-specific documentation is still coming, but this should go a long way toward helping you know what’s possible, how the system works, and what advanced configuration is required to access some of the nicer new features.
And now we have task developer documentation!
New commands and command handlers docs here: Introduction :: Concrete CMS (which is required reading for the following)
And new task developer documentation here: Introduction :: Concrete CMS