The app lacks document support

The basic functionality of the app is in place. However, it is not possible to send any more documents to the Mac App. Only to other platforms
So far I could manage all my documents in one go, independent of platform. Now, I need to do things differently for the Mac. I cannot even download the documents to the mac anymore!?
This information was also strangely hidden in all descriptions. Only on some forums I was finally able to track down the confirmation.
- This is not customer friendly.

032180 about Kindle Classic, v1.12.4