Hey @jorroll, thank you for raising this issue, I'll add it to the project tracker for further investigation.

We got a similar need and it would be great to have this option

Yes, this is super important.

Workaround: The generated view query can be manually edited to get fields from 'path_params' instead of 'data'.

...
FIRST_VALUE(JSON_EXTRACT_SCALAR(data path_params, '$.classId')) OVER(
PARTITION BY document_name
ORDER BY
timestamp DESC
) AS classId,
...

Having this in the script would be great. My suggestion for the schema json:

{ "name": "classId", "type": "string", "source": "path_params"}

This is much needed indeed. I do have a Firestore structure with sub-collections and need this for an easier join between master and child documents.

I did add my path wildcard as a field manually to the view by just like @rahulsekar mentioned pretty easily.

Seems like this feature doesn't exist yet. Would be great to have it.
I'm thinking of an alternative approach, where I create another extra view that maps parent_id (parent collection) to child_id (child collection). This obviously assumes child collections have unique identifiers. Then I can join both tables to get the "path_params" id