Hi! 
I have suggestion for Shopify’s developer description of InventoryLevel in the REST Admin API.
You should add a description for how to get the location id’s for a product variant.
I had to rely on external resources to provide an answer for my project.
This is what is missing: xx-1234.myshopify.com/admin/api/2022-07/inventory_levels.json?inventory_item_ids=[insert here].
Hope this will help others in the future:)
Have a great day!
Kind regards,
Gus