How to use FLOW to add a custom item to an order?

[crowshead]

How can i use FLOW to do the following:

1. Customer make an order for sku 100

2. FLOW recognizes sku 100 and then adds a CUSTOM item to the order call "wiget" at $0.00

How do i do this?

[PaulNewton]

Use the add-order-line-item action 

https://help.shopify.com/en/manual/shopify-flow/reference/actions/add-order-line-item 

Note this is a one way operation there is no  remove-order-line-item action.

https://help.shopify.com/en/manual/shopify-flow/reference/actions 

There is the send-http-request action but requires api knowledge.

You would need an app if there are situations where an item may be added but then has niche cases where it needs to be automatically removed;  such as multiple add-line-item flows creating orders the business does not want to fulfill. 

[crowshead]

the only problem with that is that it also adds in the price. I want the item to be added at no cost

[paul_n]

You always have the option of calling the API directly using Send HTTP Request. 

[FutureAndAHope]

I am trying to do the same thing as the original poster. I am unsure how to use the API to add the product. Is it possible to add an example? From here Edit existing orders (shopify.dev) there appears to be a two step process.