At the moment, it’s not our primary goal, because tasks can be used more or less the same way as notes.
However, we’d like to support VJOURNAL, of course. But I think creating a new notes app (cloning OpenTasks) would only be the last resort, and who will maintain it? I think it would be much better to cooperate with one of the already existing notes apps. I have seen some good ones. Unfortunately, most of them had only “notes” and not “note books” (folders which contains notes).
If you’re really interested in this feature, would you like to check who of the existing open-source notes apps would like to integrate with DAVdroid?