@ACCENRAJSEKHAR

I believe in Theme-Cosmos there were changes.  The report definition pzGetPortalLandingPages only makes use of UI pages class to filter the listview pages related to it

The pages dropdown option is disabled in the latest versions for hybrid applications(still visible in non react based apps) and if the users want to create pages in the app studio for hybrid applications they can use the below links for the reference.

To create pages from app studio you can go to Channels -> Select channel where you want to add ages (ex. User portal).

https://docs.pega.com/user-experience/87/hybrid-mode

https://docs-previous.pega.com/user-experience/85/creating-landing-page-application

https://docs-previous.pega.com/user-experience/87/organizing-main-navigation-portal

For Pega 8.8:

https://docs.pega.com/bundle/platform-88/page/platform/user-experience/organizing-main-navigation-in-portal-1.html

https://docs.pega.com/bundle/platform-88/page/platform/user-experience/creating-landing-page-1.html

Please can you also read the Resolved Issues for your specific Pega Patch:

Support added to use dynamic class name for Portal harness After creating a custom landing page and adding it as a default page, clicking the Pega Logo generated the error message "Failed to load harness: Failed to find instance Data-Portal.TestLandingPage of type Rule-HTML-Harness". This was traced to pyPortalNavigationHeader having the class name hard-coded, and has been resolved by replacing the hardcoded class name with the dynamic value D_pzDynamicNavigationPages.pxResults(1).pyClassName.

BUGS for this issue:

8.7.6: BUG-815290, INC-A5884 

8.8.4: BUG-815292, INC-A5884 

23.1: BUG-815289, INC-A5884  

eg Resolved Issues Pega 8.8.4

@SriHarsha Anika as you provided some input in a post a year ago here, please could you respond to this user's issue?