There are no plugins for Hugo as currently there is no API.
We do have Custom Output Formats that can be used in various scenarios.
@divinerites above offered a working example for a simple Schema Setup
But for the complex situation you describe, structured data that is written as complex HTML in the middle of a page’s body and then somehow loop through it to generate the Schema, that is not how things work in Hugo.
The .Content variable that holds the body of a content file is a single variable.
There have been workarounds about splitting .Content in this forum.
However looping through the split Content sections to populate a faq or other schema?
It can probably be done, haven’t really tried, but it probably won’t be clean or easy to achieve.