Which addition of the UEFA European Championship is the 2018–19 UEFA Nations League part of the qualification for?
2018–19 UEFA Nations League:  The competition, which will be held from September to November 2018 (pool stage) and June 2019 (Nations League Finals), will also serve as part of the qualification process for UEFA Euro 2020, awarding berths in the play-offs which will decide four of the twenty-four final tournament slots.
i don't know