@AbhishekC1725 When source of a Data page is a Report Definition and sub-report is used in Data Access tab for source Report Definition, the columns sourced from subreports are shown under pxResults().pxPages(W) in the Datapage. The subscript W in pxPages is the Prefix used for subreport join in the source Report Definition.
@sahav Check if there is a data traceability feature that shows connections between defined sources and pages/classes. This can help visualize dependencies.