Update index.md Anonymous Predictive Traits limitation

Author: lizkane222

src/unify/Traits/predictions/index.md

@@ -60,6 +60,8 @@ Segment doesn't enforce data requirements for predictions. In machine learning,
 
 You can create predictions outside of these suggestions, but your results may vary.
 
+Currently Predictive Traits are limited to non-anonymous events, meaning an additional external_id other than anonymousId must be included in the targeted events. If your team would like to create Predictive Traits based on anonymous events, please reach out to your CSM, providing your team’s use case for creating an anonymous Predictive Trait, and the conditions for the Predictive Trait.
+
 ### Likelihood to Purchase
 
 Likelihood to Purchase is identical to Custom Predictive Goals, but Segment prefills the `Order Completed` event, assuming it's tracked in your Segment instance.