I can give you some insight. Leaderboards are usually part of an Online Subsystem. I don’t know how Playfab is integrated into Unreal, but Steam for example is integrated as an online subsystem. If Playfab has its own online subsystem, then you just have to call the proper functions from the Leaderboard Interface like so:
IOnlineSubsystem* OnlineSubsystem = IOnlineSubsystem::Get();
if (OnlineSubsystem)
{
IOnlineLeaderboardsPtr LeaderboardsInterface = OnlineSubsystem->GetLeaderboardsInterface();
if (LeaderboardsInterface)
{
// LeaderboardsInterface->ReadLeaderboardsAroundUser ...
}
}