It is very common that merchants are using Shopify metafields for their products and variants. If you want to show Metafields value on the labels, then you need to go to the label editor and set "Link to" to SHOPIFY_PRODUCT_META_FIELD or SHOPIFY_VARIANT_META_FIELD for each element you want to display metafields.

On the label editor, once you select "Link to" to metafileds connector. Then, you can set the namespace and key for the label element.

On Shopify Setting Page, you could find metafields and their namespace & key. Back to the label editor and enter the same value as the Shopify Metafields Setting Page.

Once you enter the same string as Shopify Metafields Page. The label element will combine the metafield data and display it on the label.