Dynamically population attributes in domain for out of box only, automatic addition of attribute in custom domain is not a feature provided by Clarity. Now lets take an example of Project Management Domain you will see a section called Custom and that will populate all the objects and its attribute which are child of Project Object.
To confirm that I created a Object called "Suman Custom Object Test" and ensure to include in DWH. Created an attribute called " Test Domain Rollup" and included that in DWH and ran the full DWH job
Once the job completed i could see the custom attribute under the Project Management Domain, also you can query a table in clarity called DWH_META_COLUMNS and for any attribute where JS_PROCESSED is 1 that means it will be populated to out of box domain once you follow the above steps.
Release : 14.x, 15.x
Component : CA PPM SAAS JASPERSOFT
If you want an attribute to the included in Out of Box Domain for example Project Management Domain