NaturalONE defers its searching functionality to Eclipse, which is pretty good at it. Use the Search entry on the menu bar to get started. Within the editor view, use ctrl-f to find/replace.
Eclipse has no command line interface and NaturalONE is an Eclipse plug-in. Software AG has made it clear they will not provide such functionality in NaturalONE. There is an exception for those of you using a mainframe Natural server: Natural Command Console for Mainframes. It is limited in functionality, but may suit your needs. A previous thread touches on this. Next Prompt For more information click Help → Help Contents. Then search for mainframe console and open Using the Natural Command Console for Mainframes.