I made up a Meta Data Example action that sort of addresses this need within the existing feature set of Drafts.
findSourceDraft functions in the script could be reused in other actions to, for example, locate and include the meta data content in an export.
From the action description:
Example action demonstrating how one could auto-create related meta data drafts to enter notes about the current draft, and flip back and forth to that meta data draft using an action or keyboard shortcut.
The first time this action is run on a draft, it will create a new draft with the tag
metadata, filed in the archive, with front matter like:
# Draft Meta Data
Title: <Draft Title>
Source: <Link to Source Draft>
You can then enter notes about the draft in this metadata note.
If this action is run again from the meta data note, it will look for and open the source draft. If you are on the source draft, and a meta data draft exists already, it will navigate to it for adding additional notes.
In use, assigning a keyboard shortcut to this action would easily allow you to toggle back and forth between the draft and it’s meta data.
The meta data note, once created, could also be opened in a separate window for editing next to the source draft on iPad or Mac.