Combining labels that's been captured with regex

Is it possible to combine captured regex groups into a single label on the promtail config? Something like this:

pipeline_stages:
  - match:
      selector: '{app=~"grafana|prometheus"}'
      stages:
      - regex:
          expression: ".*(lvl|level)=(?P<level>[a-zA-Z]+).*(logger|component)=(?P<component>[a-zA-Z]+)"

      - labels:
          level:
          component:
          custom_label: <level>_<component>