I wouldn't keep spamming, it's rare to get a response about app export things. From reviewing the documentation on Game Center it looks like it is probably possible. Show Leaderboard probably shows the default one or one defined by ID. If you've made a set then there will be a way to show the set.
For as long as my issue is unsolved I will keep on asking for help, that's the purpose of this forum, "help each other"
It may be rare to get a decent answer on a question like this but it's still worth trying since i haven't got a better solotion.
It does show the default leaderboard but you can't put the leaderboard set to default.
As we all know, the Game Center plugin on Canstruct 3 has the trigger (show leaderboard) which asks for a specific ID,
the problem is that on Itunes connect there's no way to make an ID that is connected to the manu where all the leaderboards are displayed.
It only shows one of the ID's/Leaderboards.