What does filebeat's multiline tool match

Elastic Stack Beats
4

I found the solution for my case. This is now my filebeat.yml file

filebeat.autodiscover:
        providers:
            - type: docker
                templates:
                    - config:
                        - type: container
                            paths:
                                - "/var/lib/docker/containers/${data.docker.container.id}/*.log"
                        multiline.pattern: "^\t"
                        multiline.negate: false
                        multiline.match: after
    logging.metrics.enabled: false
    output.logstash:
        hosts:
            - logstash:5044

I had the three multiline lines at the wrong "level". Originally they were right between the - type: docker and templates: lines.