I'm currently trying to update the Dragonmark of Shadow race, so that the bonus die granted to Performance and Stealth checks is a d6 instead of a d4. I changed the text of the Cunning Intuition feature, but there seems to be no mechanical element to the feature. However, when I roll a stealth check, a d4 is automatically added to the result. So there must be some place where I can modify this. Could anyone help?

DDB doesn’t automatically add that d4 to the roll, you must be using a browser extension such as Beyond20. You’ll have to contact them.