When I add a new Data Input in the Splunk Manager, the index field says "default".
However, when I look at all of my indexes, there are various names.
Now it seems I can change the default index for a specific role to be whatever I want, but when I first install Splunk, which index is the default index?
When you first install Splunk, the default index should be the index called "main". And since it is the default, you do not have to specify it when you search across your events. Essentially, "index=main" is implied with all of your searches.
Incidentally, the default indexes searched is a list, configurable in authorize.conf, which for users defaults to "main", but for power and admin defaults to both "main" and "os".