Thanks but I don’t use that either.
I doubt it’s liked to a specific integration.
From How to use secrets in automations.yaml , it looks like secrets are not (no more?) allowed in automations.yaml
That’s not true. https://www.home-assistant.io/docs/configuration/secrets/
However from that topic you linked to I see this:
This is the reason I saw the error. I accidentally clicked the Edit icon instead of the Trace icon on a automation.