Osclass Location related support required

Hello everyone,

Does anyone know how can we have a 4th column in Osclass Location where we can make a list of localities inside city.
Right now Osclass Location has this option: Country > Region > City
And I want to make it like this: 1.> Country > Region > City > Locality or 2.> Region > City > Locality

I know there is City Area available but that is to take manual input from user while posting their listing but I want that every users can search listing by entering city area instead of searching listing in entire city.

Anykind of help will be appreciated.