Is there a way to add/edit the list of Metadata Sets? Not presets, but the sets that come pre-defined. I want to add an extra field and maybe remove a few others. "Default" is close to what I want, but not close enough.
The Metadata-Viewer Preset Editor plugin makes it easy to construct new custom metadata tagsets. If you're technically minded, you can download the LR SDK, and there's a section in the documentation that explains how to edit the config files yourself. (But expect to spend at least an hour or two climbing up the learning curve.)
Thanks, I used Jeffrey Friedl's plugin that you recommended, and it does the trick!