In Pega 8.4, the "Advanced" block of the first screen in App Studio's New Data Object wizard includes a "Reuse assets from" drop-down which lists the Data classes available in the current application layer (of the current branch, if you are using Branch development).

The selection made here determines the pattern-inheritance superclass of the new Data Object.

Discussion on this topic was sought from the LSA Data Excellence (Pega 8.4) webinar conducted in July 2020. The webinar and its full set of discussions that arose from it are available at LSA Data Excellence: Webinar, Questions & Answers.