private Path resolveExtensionPath(Path docPath, Object p) {
        String path = (String) p;
        Path firstPath = Paths.get(path);
        if(Files.exists(firstPath) && Files.isExecutable(firstPath)){
            return firstPath;
        }
        Path secondPath = docPath.resolve(path);
        if(Files.exists(secondPath) && Files.isExecutable(secondPath)){
            return secondPath;
        }
        return null;
    }
Set additional attributes in the GUI.
Only needed if child class has additional elements which are not shown
in the parent class.
@param childClassAttributes
@see AsciidoctorConfigBase#load(Path, ActionEvent...)
src/main/java/com/kodedu/config/AsciidoctorConfigBase.java