Northern Trail Outfitters wants to connect relational data into their Journey without overloading the entry...

Data Designer is the dedicated Contact Builder workspace where relational connections between data extensions are modeled and configured — establishing one-to-one or one-to-many relationships on a common key between the journey ' s entry source data extension and additional, related data extensions holding supplementary attributes. Once these relationships are defined in Data Designer, that related data becomes available for use in Decision Splits, personalization, and other journey logic without needing to physically merge every related field directly into the entry source itself, which is precisely the ' without overloading the entry data ' requirement: the entry source stays lean and purpose-built for triggering journey entry, while richer related data remains accessible on demand through the modeled relationships rather than being duplicated into a bloated single table. ' Data Relationships ' (A) is a plausible-sounding but not the precisely correct, named Contact Builder feature — Data Designer is the actual product name for this configuration workspace. ' Entry Source Data Extension ' (C) describes the object being connected to, not the tool used to establish the connection. ' Contact Configuration ' (D) is not a recognized, standard Marketing Cloud feature name for this purpose. Reference: Data Designer, Contact Builder Relationships.