It's possible to create one index from an xls.?
I don't know of any direct routes, but you could export your XLS to CSV and use any of the available importers/rivers for that.
I think the file system river (FSRiver) might use Apache POI to read XLS
Rivers are now deprecated, but creating your own code is easy. If using
Java, the Apache POI library is probably your best bet.
There is an XLS plugin for Logstash in the community that you could use: https://rubygems.org/gems/logstash-input-xls/