To forecast at the product hierarchy level, the system administrator needs to create a flow that modifies the Advanced Account Forecasting to include the product category as a custom dimension. The product category is a field on the product object that defines the hierarchy of products. By adding the product category as a custom dimension, the system administrator can enable the regional sales manager to view and adjust forecasts based on different product categories. The flow should use the Data Processing Engine to aggregate data from orders, opportunities, sales agreements, and other custom objects by product category, and then use the Calculate Advanced Account Forecast and Update Advanced Account Forecast Set Partner invocable actions to generate the forecasts. The flow should also assign the appropriate forecast set to the regional sales manager based on their role and region. References: Create Holistic Forecasts with Advanced Account Forecasting, Example: Generate Forecasts Across Multiple Regions with Advanced Account Forecasting, Calculate Account Forecasts Using Flows