Could you elaborate on what you mean when you say "export in Excel"? Splunk can easily output in CSV which Excel can read natively; would that do?
Well you have the default and built-in "search-app" ?
Have you check the contents of: apps.splunk.com ?
The odbc connection app form apps.splunk.com will help you get your results and searches from splunk into excel .
The searches, either based on some criteria or ad-hoc reporting is what you have to do .... but it is fun! 🙂
odbc-connection: https://apps.splunk.com/app/1606/