Expanding page navigation tree

In WPS portal, if you have pages like

Top page Portal
 On click of which you have
 Page Finance
    page Polices
    page Reports
  Page Marketing
    page Sale report
    page Product listing

And when you click on page Portal, it shows Page Finance and Page Marketing only.

If you want something like, on click of Page Portal, all the pages including child should get expand. To do this you need to set some custom property against WP ConfigService on WAS.

By default, navigation tree expansion is not set.

To set this property, login to WAS and

1) Click on Resources - > Resource Environment -> Resource Environment Providers
2) click on WP ConfigService and then
3) click on Custom properties
4) click on New and provide navigation.expansion.defaultstate for Name field
and true for Value field.
5) click Ok and then Save configuration.
6) Restart portal.

Test your page navigation tree, it should expand all the child pages under any parent page.

Only issue i see with this setting is, it will apply to entire portal.

Ideally, there should be some way to apply this setting at theme level only.
if any one knows, how to apply this setting at theme level, that would be great. feel free to comment.