Firstly, you can choose which logs to ingest into splunk. So if you haven't added the logs, it is not available to ES.
Second, ES uses a lot of tagging and only event types that have been tagged correctly will be looked at by the ES app automatically. So within the built in reports other sourcetypes will be ignored.
But from within the app, you can search ALL your data and use any of it to create correlation searches or notable events, or even tag it to appear in the reports.
As for the parsing, if it is text format and relevant to security, it can be added but some is easier than others. Read the Data Source Integration Manual for ES.
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