Need help with conditional split in a flow based on Shopify order tags

@BPD - Assuming you’re using the standard Klaviyo / Shopify Integration, then the Shopify Order Tag is in the Placed Order or Fulfilled Order event, so you should use a “Trigger Split” in your Flow and set the Split to contain the tag you want to branch on:

See here:
 

If the Order Tag is not set at the point of purchase (Placed Order), then I also recommend you consider trying to build your Flow based on the “Fulfilled Order” trigger instead, since sometimes the Shipping info (tag) happens at the point of purchase.

You can also inspect each of the Events to see what “tags” are available for each Event in your Analytics → Metrics → Activity and click on the “Timestamp” which would show you the details like this:
 

In this example, there is no “Order tags” - so if your Flow Trigger wa based on “Placed Order” - this particular order would not match the Trigger Split since there are no tags present at the point of purchase.  
 

Hope this helps!