GPSBabel features may change rapidly. You should be sure to use the version of the documentation that goes with the version you are using.
The development version of GPSBabel is used by developers and for beta versions.
GPSBabel 1.8.0 was released on 2022-01-03.
GPSBabel 1.7.0 was released on 2020-07-06.
GPSBabel 1.6.0 was released on 2019-05-02.
GPSBabel 1.5.4 was released on 2017-01-02.