I've now gone through your pull request and found the following problems.
If I enable delivery pipeline configuration for a job, omit stage and task name but mark the task as hidden, the job will still be visible in the pipeline.
If the stage and task names are present and the job is marked as hidden, the stage will still be shown even though no jobs for that stage are visible, which is ambiguous and looks weird.
I'm still not convinced about the feature in general as I don't find the visualisation intuitive, if jobs are hidden. I understand the use cases, but I'm afraid it will cause unnecessary confusion if a hidden job fails or if a hidden job has additional logic to it which should be considered from a pipeline point of view.