Thanks @bpj for a working solution.
For a newly created docker container, the modifications were:
traefik.http.routers.docker-cert-test__stg_web.rule=Host(`domain1.com`, `domain2.com`)
- >-
traefik.http.routers.docker-cert-test__stg_web-secure.entrypoints=websecure
- >-
traefik.http.routers.docker-cert-test__stg_web-secure.rule=Host(`domain1.com`, `domain2.com`)
Initial tests have this working perfectly after re-deploying the container. Naturally Wappler does rewrite this file if changes are made to the target, so care will have to be taken to re-modify with the added domains when making changes to the target, but that’s not a huge ask. Re-deploys work fine.
Thanks guys.