The little green lines are handy for predicting their direction, however the training area is so small and there are so many manoeuvres being made that you couldn’t keep track very easily.
Even if there were proximity alerts in your EFB with audible alarms, you wouldn’t know from direction the other aircraft was, because you may both be turning.
I know FLARM has a complex algorithm for this, however I wonder how the gliding guys deal with it… I guess they west a parachute for this reason ! (Amongst others)