@DanJacobs I’ve done this exact use case before.  For my implementation, I did use Shopify Flow to “tag” both the order and the customer as High Risk in Shopify as you implied. Once a tag is in Shopify, it carries over to the “Shopify Tag” custom property in Klaviyo where you can use it for Segments for part of your Flow Branching Logic. 

For extra credit, with Shopify Flow, you can also push a “High Risk” custom event activity in Klaviyo as well, but we didn’t do this part yet.  You would probably need an intermediary software to format the event properly before sending this to Klaviyo.  Or perhaps you can use some middleware tool like Zapier or other tools like it.

The internal email was using Shopify Flow’s notification, but now with the Notification Action, you can do it form Klaviyo too.  We didn’t send any emails to customers, since we suspect many of the High Risk orders may actually be fraud - but if you wanted to, you could build a Flow Trigger based on the metric “Placed Order - Filtered for Orders tagged “High Risk”.

Also, one thing to watch out for depending on how your setup with the orders flowing to the warehouse, is orders accidentally going out before someone catches it. We’re on Shopify Plus and have it set up so that the payment is not captured on high risk orders until someone reviews it an manually captures it. 

Had instances earlier in the process creation where customer service was notified with the auto message, but the order flowed to the warehouse before we could stop it and it went out 🤦‍♂️