Docker containers send their logs to stdout as a best practice rather then a file so that the log strategy can be set for the system as a whole. In HAOS or supervised HA the strategy is journal logging. See this guide for how to get to and browse the system journal:
Your logs for core, supervisor and all addons will be in there. Logs for addons will be tagged with the addon slug.
Additionally there are a couple other ways to get to your logs from the CLI. Easiest way is just this:
ha addons logs a0d7b954_nodered
That only shows you the logs since the last restart of that addon though.
If you have the Terminal & SSH addon installed (the one from the community repo) with protection mode off or have access to the docker CLI via some other means you can also do this:
docker logs addon_a0d7b954_nodered
Which will show you all logs for a container with that name across restarts. Add -f to follow/tail it.