Is it possible to gather Windows event logs to indexer server by way of NAS Server which were transferred from any monitoring Windows server? This is under the condition of not deploying a Universal Forwarder on these monitoring PCs.
Not sure I understand, but if installing a forwarder is not an option, the usual approach is to have source systems send their event logs to a Windows event collection server and install the forwarder there.
Remember, event logs are binary and we need to properly format them before indexing into Splunk, which is what the executables do that ship with the Windows UF.
Take a look here for a description on how that works.