You can activate or deactivate the "Model Optimization" add-on in the Add-ons tab of the model's "Base Data".
A green dot in front of the add-on description means that a license is available. An orange or blue dot indicates that you can only use the add-on as a demo or trial version with a limited range of functions.
After activating the add-on, the Optimization Settings function in the "Calculate" menu becomes available, where you can define the attributes for the individual variables in the Global Parameter Settings.