Dynamic Grouping was previously available only in Merchandise Plan. It is now also supported in Assortment Plan Reporting. In addition, any dynamic grouping created in one module can now be reused across other modules, provided the relevant attributes exist in those modules.
What is Dynamic Grouping?
In many planning scenarios, users need the flexibility to group entities based on business context rather than fixed hierarchies. Examples include grouping vendors by strategic importance or brands by performance tiers. These groupings are often ad hoc, user-defined, and difficult to support within rigid data structures.
The goal of the Dynamic Groupings feature is to give users the ability to create, manage, and apply flexible, custom groupings of attribute values such as brands or suppliers directly within the planning interface. These groupings behave like hierarchical levels, enabling aggregation, filtering, and value spreading, all without requiring changes to the underlying data model.

Read more on this help article here.