In Splunk Enterprise you can set the default search index per user. In Splunk Light you cannot it seems?
I read another post which said you can edit the \etc\system\default\indexes.conf file and set defaultDatabase=mynewindex
And yet another post that said you should create \etc\system\local\indexes.conf file and set defaultDatabase=mynewindex
I tried both and restarted Splunk after each, but neither have made a difference.
The Splunk Light doesn't support role customization (the default searched index is role/user level attribute).
Also, you should never change any configuration from folder
create new file \etc\system\local\authorize.conf and add following stanza, to make that index searchable by default for all users:
[role_user] srchIndexesDefault = main;my_new_index
If you want to restrict it to only Administrators, then use following stanza instead:
[role_admin] srchIndexesDefault = main;my_new_index
and then restart Splunk Light.
Changing indexes.conf, will only change your default index when importing data.
Also, @somesoni2 is correct, you should never update conf files under default, as they will get overwritten upon updates.
Hope this helps.