IQTELL.com has 'virtual calendars'. Anything with a due date appears on the calendar automatically. Unfortunately you can't sync these calendars with any other app. Alternatively you can also add an action to an actual calendar manually.

Yes, I have been looking for a split pane drag and drop solution too. No dice. Regardless, IQTELL is so powerful though that no matter when I find an elegant solution, it falls short in other areas anyway.