I believe all the Swagger v1 and v2 APIs were renamed OpenAPI a couple of years ago, so if you're using one of those, look through the DevTest v9.1 documentation for "swagger", because I believe the creation of baseline tests from Swagger specs has been in Portal from DevTest v8.5.
If you're referring to OpenAPI v3.0, it was only introduced last year. It might be that it's stable enough to use now, in which case feel free to create an idea to add support for it.