Metadata Plugins and the "Download Metadata" bulk action

Hi,

I'm creating a plugin that will pull metadata from RPGGeek for a Roleplaying Game library. I've got it working for my own use, but I've noticed an odd thing about the behavior of downloading metadata. I don't see a way to download series_index that is passed from the parser. If I manually download metadata on a magazine issue, it populates fine, but it does not appear to be an option for the bulk download. Is there a place to set that, or is that something that's just not available?

Thanks.