I need to update the available quantity for a variant to which I only have the ID available.
From my understanding I can get the InventoryItem ID easily with a call for the variant data. Now to update the InventoryLevel I also need the location_id but how do I get that one? How can I update the available quantity?
Below is a GraphQL API example of how you can query a product variant's inventory item's inventory levels to see on-hands by location. Once you get your locations then you can issue a GraphQL mutation request to change the on-hand availability for a particular location. As for the mutation, it's discussed here --> https://www.shopify.com/partners/blog/multi-location_and_graphql.
Hope this helps!