This addresses one of the larger gripes that has existed since the Mario Maker series began. You've long had the option to share completed levels with friends through codes, but the most you could do is watch your friend play through a stream. This lets you share the experience as it happens, and might make it easier to tweak levels based on immediate feedback.

Mr. Tezuka has confirmed that the ability to play online multiplayer with friends is coming to #SuperMarioMaker2 in a future update. Stay tuned for more information to come. https://t.co/oxGuEcJ8Om pic.twitter.com/1AfK1vEGIe — Nintendo of America (@NintendoAmerica) June 11, 2019