It woulde be nicer if when dragging a card, instead of just a line with shadow, a square showing the new insertion point was displayed.
You can override the CSS styles to make the target shadow more prominent.
Unfortunately, it is not possible to move the existing cards during drag and drop to make space for a bigger target position indicator.
Could that be implemented in the future like other kanban libraries?
May be you could have a fixed box dimensions just to hightlight the move.