I think I have found a bug in the Rest API when trying to get all jobs of a specific workflow with the curl command:
curl -s -H 'Accept: application/json' https://circleci.com/api/v1/project/<project>/<workflow-name>?circle-token=<token>&limit=100 | jq '. | select(.workflows.workflow_id == "<workflow-id>")'
With this command I only get all sequential jobs. If I have 2 or more jobs running in parallel, I only get one of those jobs.