I'd love this feature too.
I had been using CardFlow+ for the Ipad for designing tabletop dungeons, towns, and sessions with a pencil for a while now. The capacity to draw on cards, on both sides, drag and drop them around and then use the canvas as a white board to connect them, has been invaluable for brainstorming and organizing.
If you can consider adding these functionalities it'd truly bring the app to new levels.
Here are some examples of how I use it:
(Town map. Cards are notable places with basic info on them, red lines are what is connected to what)
(Zoom in)
(An example of another card, for a dungeon room, in this case a combat. It shows a diagram of the combat room and the monsters involved. In the other side of the card I had the rewards for the combat.)
Once again, thanks for your hard work. I use your app daily and I love it.