Because every quest has dozens of stages, you must know the exact used by the developers. For example: Guide :: The Witcher 3 Console Commands: Ultimate Edition
⚠️ : Completing a quest via console bypasses normal triggers, choices, cutscenes, and rewards. It can break later quests, lock you out of achievements, or leave items/characters in wrong states. Always save first. witcher 3 complete quest console command
Some players prefer a simpler command that often works for main story quests: Because every quest has dozens of stages, you