This is a link to my question…
I apologize! I’ve updated my comment to link to the correct answer about metafield IDs.
I need a metafield ID to add a value there, don’t I?
Metafields (like all other Shopify resources) do not have an ID until they have been created. The ID that you’re using above is a definition ID.
Are you saying if via API I should add a metafield itself to all the products created and then update its value?
My suggestion would be to create a metafield definition using the boolean type. This will not add metafield values to products. It will provide validation for values that are added as metafields (to the namespace and key) in the future. The definition will also show the metafield on the product UI.
Setting metafields and pinning them from UI won’t actually set them to products?
Only pinned metafield definitions will show up on the product page UI.