Defining the Product for which the Flow should be triggered
To define the products for which the flow should be triggered:
1. Go to Flows on the top bar.

2. Click on the New Workflow.

3. Select the Reorder Flow.

4. Click on Edit Flow.

5. Click on the 1st element - Trigger Condition

If you want to trigger the flow for all variants of the product
(i) You will have to set the trigger condition as {{context.order.product_id_list}}

(ii) Mention the product ID here.

The product ID is available on the Shopify admin page and can be seen by clicking on the specific product. The highlighted part is the product ID.

But, if you want to trigger the flow only when a particular variant of the product
(i) You will have to set the trigger condition as {{context.order.variant_id_list}}

(ii) Mention the variant ID here.

This variant is also available in your Shopify admin page and be seen by clicking on the specific variant and then clicking on edit. The highlighted part is the variant id.
