How to define different AHU airflow rates for cooling and heating in DesignBuilder?

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I am modeLling an Air Handling Unit (AHU) in DesignBuilder. In my project, the AHU operates at different supply airflow rates during cooling and heating seasons. However, in DesignBuilder’s AHU sizing interface, I only see an option to define one supply airflow rate at the system level

How can I specify different design airflow rates for cooling and heating periods at the AHU level in DesignBuilder?