De Vries' extract
witcher-3 — Cheat Codes
There isn't much on file about this. As De Vries' Extract was a potion in the first game, it's possible this was meant to have a similar effect to allow Geralt to spot concealed enemies.
Syntax
De Vries' extractExample
De Vries' extract💡 Notes
Source: The Witcher 3 cut content