Wow, I love seeing a response from you, I've followed a few of your tutorials and you have revolutionized Godot for me.
Changing the arrow mid flight is definitely a more demanding puzzle timing wise, but everyone I've seen tries to do it the harder way by making the heavy arrow small, instead of scaling a normal arrow to be heavy and falling onto the target. I'll likely look to see how I can make it simpler, but I can do that for a lot of levels.
I'm glad you enjoyed the game :)