It would be nice to mark inputs/outputs that aren't in use anymore?
Situation now is:
Yes, somehow not-in-use is flagged, but C doesn't look different from A and B ...
To tackle the problem from a different angle:
A (output) and B (input) should be marked differently, greyed out works for entirely-not-in-use.
You can't and also don't want to just delete the greyed out A or B though.
What might help (but may not be needed with the actual feature in place) would be to highlight all inputs/outputs that belong to the selected counterpart ...
IIRC there's also this proxy-feature which I ran into once by mistake, might also help with that.