The copy/share address from constituent is an option in the databaseview when linking a relationship to an existing record. The same functionality does not exist in NXT, so our data entry is still a lot of back and forth between database view and web view.
The issue is that you can "Share" an address when adding a new relationship, but you cannot copy without sharing like you can do in database view. We use the copy without sharing feature very often for individual to organization relationships. We do not want the individual to have the organization address shared/linked to their record but we want the address to be copied.