Something I noticed while watching a video today of an actual modular system being used is that a small but perceptible part of the experience of using a modular system is that you can hear the cables loudly snap when you press them into place.
I know it's a little thing but it would help with the atmosphere if the VST made a snap sound when you click on the output and connection and release over an input connection.
https://www.youtube.com/watch?v=9F3Om7tPuYc