@gordenkem you need to elaborate a bit more, extractions can be done both at index and search-time.
the extractions are set at spec level with combination of props & transforms (optional in some cases).
the spec you could set is source, host, sourcetype... if you have them common across the said index, sourcetype yes it is otherwise you have to clone the config.
https://docs.splunk.com/Documentation/Splunk/9.0.1/Admin/Propsconf#GLOBAL_SETTINGS - Read <spec>
For example - I have index= a , index = b they both having a sourcetype = web:logs, if you set extraction to [web:logs] that applies to both indexes.
if both indexes having common sources [source::/log/webserver/logs/web.log], then setting extraction at source level apply to both indexes... you have to me mindful about source, sourcetype and host combo while setting. As long as the data follow same structure that should be fine otherwise you will end-up seeing inconsistent values in extracted fields.
