No, Splunk is a time-series database - it will read events and assign a timestamp to them once. Events that are indexed will not be modified - if you make changes to existing data that Splunk has already indexed, Splunk will interpret that as that the whole file has changed and its contents needs to be reindexed.
Um, I don't follow. I'm talking about where you edit Data Inputs and select, File, Events Log, syslog, etc... When I click on one that I created (to edit it because I made a mistake), after I hit save, instead of updating the one I was editing, it just creates a new item.