Im going for another dressage test soon and I dont know whether I need to plait up or not (perfably not, it's quite tedious ) I've gone to a show plaited up before though. My pony is a welsh sec DxTB by the way
You don't have to, but if you can you should, as it is polite. If it's a very low key, unaffiliated event run by a local yard, then it's not really necessary, but if they are using listed BD judges it would be better to plait.
I was taught that it's an insult towards the judge if you don't plait, and I've written for one judge who makes sarcastic comments under their breath if horses come in unplaited.
If it doesn't wind your horse up then plait. If it's going to make them very excited (my big horse used to get beyond excited whenever he was plaited up as he associated it with hunting!) then it's not worth it. If you are unable to plait then be super clean and put in quarter marks.