As you might have already figured out, there has been a glitch in The Legend of Zelda: Tears of the Kingdom that actually allows you to duplicate items. Though, in the latest 1.1.2 update, this glitch was removed. See the other changes made to The Legend of Zelda: Tears of the Kingdom below.
Tears of the Kingdom 1.1.2. Patch Notes
Audio Bug Fixes
- Fixed an issue where the sound would play at an extremely high volume in certain conditions.
- Fixed an issue in the main quest, “Camera Work in the Depths”, where players could not progress beyond a certain point. Downloading the update will allow players to proceed past that point.
- Several issues have been addressed to improve the gameplay experience.