It appears that you cannot drop a grid line on top of a card-list item that hasn't got the focus.. Hovering over the intended card list item doesn't activate the card. In stead it's added to the one with the existing focus.
Is this a bug or still under development?
Situation:
Card list with a grid as details that consists of planned activities. The idea is to drag a planned item and drop onto another agenda (card). When you drag the grid line to the card list the component gets activated, but never the card.