Endpoint – Create a shipment tracking per item using REST API

add_tracking_info_per_item.php

//With this endpoint you can add new tracking info to orders:

POST /wp-json/wc-ast-pro/v3/orders/<order_id>/shipment-trackings/

curl -X POST https://your-domain.com/wp-json/wc-ast-pro/v3/orders/<order_id>/shipment-trackings 
	-u consumer_key:consumer_secret 
	-H "Content-Type: application/json" 
	-d '{
		"tracking_provider": "USPS",
		"tracking_number": "123456",
		"date_shipped": "2020-01-24",//date_shipped is optional parameter
		"status_shipped": 1,//status_shipped is optional parameter
    		"sku": t-shirt,blue-jeans //the line item (product) SKU
  		"qty": 1,1 //the line item (product) quantity
	}'	
curl -X POST https://your-domain.com/wp-json/wc-ast-pro/v1/orders/<order_id>/shipment-trackings 
	-u consumer_key:consumer_secret 
	-H "Content-Type: application/json" 
	-d '{
		"tracking_provider": "USPS",
		"tracking_number": "456879",
		"date_shipped": "2020-01-24",//date_shipped is optional parameter
		"status_shipped": 1,//status_shipped is optional parameter
    		"sku": t-shirt,blue-jeans //the line item (product) SKU
  		"qty": 1,2 //the line item (product) quantity
	}'	

This API does not work correctly,
First, it does not update the tracking in line, the same way as you with the widget in word press,
It picks up Sku from the parent rather than from the variation item line
When calling Get Shipment, it does not say which sku was shipped