Interesting post. I’ve begun creating an app for nextcloud tasks (which basically is caldav tasks aka VTODO’s). I posted earlier with some questions, and your post provides some insights in the answers to my questions.
I did look at nemo-qml-plugin-calendar, and concluded that it indeed does not support tasks, just events. When exploring the service by interacting over dbus I also seem to get only ‘get’ access to that service, is that expected? I’m probably missing some permission-related thing here, i’m quite the newbie in Sailfish development and still finding my way.
Anyway, implementing tasks into the calendar app is one way, but not optimal since it shuts out the community from working on it I guess. And I agree with @cryx that it makes a lot of sense to have one calendar app and another tasks app. I’m quite used to that seperation already, even in nextcloud they are different apps (using the same calendar storage backend). I’m hoping I can adapt the app i’m working on to use the nemo-qml-plugin-calendar if/when that provides read/write access to tasks, but for now the best seems to be to include the account handling / caldav interactions local to the app.