How to search for specific items in nested logs

When I search for logs with nested JSON objects like below where "combined" is an object. Some of the search terms I am using for searching this are not working.

For example when trying to search for logs with the "level": "debug" shows no results.

I couldn't find any documentaiton to

  1. make the logs searchable (indexed on the nested attributes
  2. be able to search for any term in the log

Any help with references would be great, thanks!