OH! That makes SO much more sense! Yeah, I kinda assumed that the nodes were both start and endpoints and was wondering why me clicking on them wasn't always working haha.
I think it's kinda instinctual. If there's a circle that I click to start from, and the thing I'm dragging to also has a circle, then the first assumption is that's where it goes. Maybe you could do a color coding thing and have (for example) red circles are outputs and blue are inputs, and while you're dragging an output, the inputs all have a tween to pulse it to really drive it home "hey this is something that can take that output!"