In holding patterns the accuracy of track-keeping is such that often 3, 4 or 5 a/c will be exactly over the same point at the same time. OK. one solution is for one label to be switched off for a second or so to prevent "garbling". but it doesn't solve the problem of how to display everything.
I seem to remember learning about a tool that displays the hold vertically. Using mode S maybe? Possibly part of iFACTS?
Unfortunately I then did the time honoured trick of forgetting about it when I walked out of the interview! I'm sure someone can elaborate.