Unlike the massive 3.0.0 "World Maker" update, version 3.0.3 does not add new course parts, themes, or enemies. The official patch notes from Nintendo Support are brief, stating that the update:
, updates were usually gifts—new power-ups, Koopalings, or the ability to ride a Goomba. But 3.0.3 was different. It was the quiet one. The "system stability" patch. The one that whispered that the developers were moving on. Super Mario Maker 2 -NSP- -Actualizacion 3.0.3-...