Here are a few simple additions I'd like to see. I made a pretty image to illustrate these ideas.
First, I'd like to see connecting lines highlight yellow when you mouse over the line, input, and also highlight all lines connected to a selected component. In really complicated filters you get a mess of lines and sometimes it's difficult to trace a line across the web.
Second, it would be neat if there was a node at the center of connecting lines that you could drag new components onto which would auto connect the most appropriate input/output.
Third (I didn't put it in the image), an option to turn off/bypass a component. In cases where you have a blend, maybe it would just use the A input for bypassing. Maybe this would cause issues with a bunch of components.