Can metafields be deleted?

If you need to remove obsolete metafields, you can delete them via the Metafield property - 3rd column of the interface.

Once you've selected the line of the metafield you want to delete, hit the corresponding icon on the toolbar:

You can of course select multiple lines to delete in bulk.

You can also select multiple products beforehand, to display all corresponding metafields to then mass delete if needed.