This is actually very easy. You can copy the files from the container, even while it’s not running, onto your host system to edit there, and then copy them back afterwards.
See the top answer on https://stackoverflow.com/questions/22907231/how-to-copy-files-from-host-to-docker-container for step by step instructions on how to do this.
Cool, thanks for the suggestion!
Also, h/t to getting pointed to https://www.nten.org/change/savedotorg-campaign-history … TIL!