It’s really a rather easy thing for a scripting plugin to do, as Peter says.
Here’s a demo using PythonScript; see if you can follow its logic without further explanation:
from Npp import editor city_string = ''' Sydney Melbourne Adelaide ''' city_list = city_string.splitlines() city_list.pop(0) for city in city_list: editor.replace('city', city, 0, 0, editor.getLength(), 4)