How to update same inventory for listings with different SKUs

Multiple SKUs of same product

A product can have more than 1 SKU. The physical product is the same but it has more than 1 SKU. Perhaps it has different SKUs on Amazon and Shopify.

For example on Amazon the SKU is AMZ762 and on Shopify the SKU is SHOP450. Now you want to track inventory using the Shopify SKU SHOP450. To do this you can create a bundle product of SKU AMZ762 with the component product as SHOP450. This way the inventory of Shopify SKU will be used to calculate the inventory for the Amazon SKU.

Example - 

You have 3 listings for Apple Watch Series 3. 

The SKUs of these listings is APPLE-WATCH-S3, APPLE-WATCH-S3-1 and APPLE-WATCH-S3-2

You want to control the inventory of all listings through the SKU APPLE-WATCH-S3.

Create bundle: Go to Bundles List > Click on + Add New button (Located on top right of the screen)

Fill in the details as shown in screenshots.