I am trying to add a custom label 0 shopping attribute to my Json schema but I don't get the this new attribute on my products.

I tried:

<script type="application/ld+json">
    {
      "@context": "https://schema.org/",
      "@type": "Product",
      "name": "Auvers - Van Gogh",
      "sku":"artworkid[2316]-product[canvas]",
      "mpn":"artworkid[2316]-product[canvas]",
      "tags": [{
        "custom_label_0": "Fine Art"
        }
      ],

And also:

<script type="application/ld+json">
    {
      "@context": "https://schema.org/",
      "@type": "Product",
      "name": "Auvers - Van Gogh",
      "sku":"artworkid[2316]-product[canvas]",
      "mpn":"artworkid[2316]-product[canvas]",
      "customLabel0": "Fine Art",

How to set this attribute with the structured data?

I didn't find any infos from the custom label support from Google: https://support.google.com/merchants/answer/6324473?hl=en#zippy=%2Cexample-values