This feature is not available in the way suggested above. However, data sources may be searched using the Search() function for example. Custom APIs may also be leveraged to access indexed content from Azure AD, Office Graph etc. SInce multiple data sources can be added to a PowerApp, there are opportunities to display search results across more than one source on a screen.
We we would like to hear more from you on this business scenario though. Please feel free to add comments here with specific business challenges and targets.