A standard for execution config metadata?

In one of our projects that uses nbclient, we need to allow for a *per-notebook* timeout limit (https://github.com/ExecutableBookProject/jupyter-cache/pull/48). For example, people may want a "default" limit that is relatively low, but have "that one notebook" that they know takes way longer to execute, so they'd like to embed that information in the notebook in a way that can be utilized by downstream tools.

Is there a jupyter standard for adding execution-level metadata to a notebook? Can folks here recommend something reasonable? It would be good to have some standard practices so we don't start moving in separate directions unintentionally

Start by reading the seven comments and the referenced jupyter-cache pull request, then review how execution metadata is currently discussed for nbclient. Done would require an agreed convention for per-notebook execution settings and a clear decision about how downstream tools should use it.

Written by the indexing model from the issue text.