I dont think Matillion has this feature. The best possible way is to list all the jobs in a folder using an API call and then loop through the list of Orchestration jobs.
A simple solution for this one is to create an Orchestration of Orchestration jobs and then trigger that one orchestration job , which in turn calls the other orchestration jobs. This way, you will also be able to manage the dependencies between the Orchestration jobs.
There may be hundreds of jobs with no real dependencies on one another so having a large Orchestration or Orchestration jobs might get difficult to manage.