Hi Joe, are you able to share a repo of a package and the command you are running with the plugin?
I still need to write some end-to-end documentation for this and the implementation is currently being updated per [Accepted with modifications] SE-0356: Swift Snippets. Still working on it, I hope to have the new snippet.hide/snippet.show marks and the explanation comment change from //! to //; the snippetsDirectory override, and the --build-snippets SwiftPM changes for 5.7, with slicing coming later.
You can reach me on the Swift Slack workspace as well.