How to set a Task or Communication in Compucorp new CiviCase
Silly of me. I forgot about the very clever and granular way that CiviCRM is built. Just creating a new Activity Type was not enough to have it activated in the right CiviCase.
After creating a new Activity Type (either Task or Communication), we must add these new Activities to the right Case Type that can be customised.
And voilà, it's set !