Sadly, it’s not possible to use the variant metafields as a dynamic data source. However, you can do that with a minor theme customization. Here’s the link to a related thread. Hope this helps!
No Idea if this is still something you are looking for, but we’ve foung the solution for it:
Apparantly the field you want to use a metafield in has the inpu ttype “text” - which only supports single line metafields created in the Metafields Backend. Your metafields are all multi line metafields, so they are not available to select. Either you change your metafields into single line (which means you have to delete them and then create new ones) or you change the field type in the schema. To use a multiline metafield the type has to be “richtext” (Richtext is able to use multiline metafields).
If you need help setting this up feel free to comment or contact us