While "Trackpad" dragging, PRESS space.
Don't work？
I tested it a bit more: It works when I "click-drag", ie. physically press the touchpad so that it clicks, then drag and press space. It does not work when I "tap-drag", that is, just tap the pad and drag. If I press space then, the card gets released. "Click-drag-space" is just such an awkward movement that it is not much fun to do.
Thank you for your feedback.
It seems there may be some compatibility issues with the underlying trackpad instructions for notebooks.
Are you using a MacBook?
Furthermore, we are considering changing the mechanics to first click to pick up a card and then click again to release it, eliminating the need for dragging.
Dragging on a trackpad can always be a poor experience.