The feature you're referencing is bundle order item. Your Broadleaf implementation can add a bundle order item to the cart that contains other associated order items. This is not something you manage as a merchandiser, but is instead a cart organizational semantic.
We've worked with clients that have included a customization that allows their catalog managers to create product bundle associations at the catalog level with special pricing for the bundle. We consider this a domain and admin GUI customization, which is quite common for our tool. Customization and extensibility are several of the value propositions of our platform.