You're right Max  thank you for checking that

I think the Shopify docs should be updated to make it clearer that you are NOT able to use orderEditAddVariant to add a variant to an order if that variant is already on the original order. allowDuplicates allows you to add duplicates on the calculat...

If you create a calculated order with "orderEditBegin" mutation then add a variant to that calculated order using the "orderEditAddVariant" (with allowDuplicates:true) -- I can even add the same variant twice with orderEditAddVariant, then commit tha...

I do not believe this is accurate. I am getting the same error even when I have allowDuplicates set to true.