To create a parameter, you can drag and drop the desired question into the specific panel. Once the question is placed, right-click on it and select the "Parameterize" option from the context menu. Alternatively, you can create a parameter using the "Subset" modal. To do this, first select the question you wish to parameterize. Right-click on the question and choose the "Subset" option from the list. This approach provides another intuitive way to define parameters for your analysis.
Next step is to select 'Value of a parameter'.
As soon as you do that, you can click on a button 'Create new'. After clicking 'OK', the new parameter will be visible in the parameter section.