Event types in Splunk can be manually added to the eventtypes.conf configuration files. Edit or create $SPLUNK_HOME/etc/system/local/eventtypes.conf and add your event type. You will need to restart Splunk after this:
[HttpRequest-Success] search = status=2*
Tags in Splunk can be manually added to the tags.conf configuration file. Edit or create $SPLUNK_HOME/etc/system/local/tags.conf and add your tag. You will need to restart Splunk after this:
[eventtype=HttpRequest-Success] webserver = enabled