Variant metafields not accessible from editor

I’ve created a metafield for variants:

I’ve then, in a product, within a variant, set a value on this to see it working on the front end. After this I went to the product template and tried to add it into the content (I can’t find it in the dynamic content menu):

The first image shows me typing the variant as I can’t get it through the dynamic source menu. The second image shows the error message.

How can I add these details onto my site? It doesn’t feel like it should be this hard to use variant content.