I'm wondering if it's possible to add the image description to the CombiNews post when uploading a new picture while having the latest image mode activated. If so, could you try to explain for me how to add it?

Actually the image description is shown automatically if there is one. See the 2nd entry on http://zenpage-demo.maltem.de/

How stupid of me, I didn't have any descripton, thats why it didn't show...