I also found this now very hidden feature. But still not possible to enter VISA data. „Additional Documents“ only has a document type called „Entschädigungsnummer“, which makes no sense.

Only when check-in opens you can add VISA data and have to repeat some data you gave already before! And like in Covid times I again only got a check-in confirmation, no boarding pass for my US flight. In recent months there were boarding passes immediately available (LX).That and of course the „new“ App are a terrible enhancement. My HON PA told me that the product management is still working to enable at least the majority of App (and website-) features, which the old App had!