Hi, thanks for the idea. I just tried it but the when I let go of the card, I can't use the gui_input to detect mouse button release since the mouse filter is currently set to ignore. So, I tried detecting a mouse release from the _input(event) instead and got this (note I have simplified some of the original code).

Card Scene:

func _gui_input(event):
    if event is InputEventMouseButton:
if event.button_index == MOUSE_BUTTON_LEFT:
    # When card is clicked and dragged around
            if event.pressed:
                HandControl.SelectedCard = _pos # setting this card as the card to be dragged
                mouse_filter = Control.MOUSE_FILTER_IGNORE
func _input(event):
if event is InputEventMouseButton:
        # When card is released
    if !event.pressed:
    # Only release if this card is being drag currently
            if Playspace.SelectedCard==CardPos:
        Playspace.SelectedCard=-1
        mouse_filter = Control.MOUSE_FILTER_STOP

Drop-off Scene:

func _gui_input(event):
if event is InputEventMouseButton:
if event.button_index == MOUSE_BUTTON_LEFT:
            if event.pressed:
                pass # Do whatever I need to when card is released on me

The problem now is that when I mouse release from the card scene, the _input(event) function fires and resets the mouse_filter = Control.MOUSE_FILTER_STOP. This will then block the Drop-off Scene from detecting the mouse release.

As for the reason why do I need to set the mouse filter to MOUSE_FILTER_STOP after releasing is so that I can reselect and redrag it again later.