How do you create "Applied at: Run Time" FERs (Field Extraction Rules)

In the Field Extraction interface, clicking the "+ Add Rule" button brings up a screen with Rule Name, Scope, Parsed Template (optional) and Parse Expression.  There doesn't seem to be an option to set "Ingest" or "Run Time" for the "Applied At" setting that is displayed once the rule is saved.  Highlighting the ? near that column, it states that unlimited "Run Time" rules can be created, but I can't figure out from the documentation how to create one of those.  How does one go about creating Run Time FERs?