For Categorical Variables
To add subtotals to a categorical variable, go to the variable properties menu and click the Headings and Subtotals button.
Add a new subtotal by clicking the plus sign (+) where you would like the subtotal to appear, and then drag the categories you would like to include in the subtotal to the grey area to the right of the title. Save the variables to create the subtotal.
For Multiple Response Variables
To add subtotals to a multiple response variable, go to the variable properties menu and click the Subtotals button.
Add a new subtotal by clicking the Create subtotal button, and then give your new subtotal a name. Drag in the subvariables you want to include in this subtotal, and then click Done. Subvariables you no longer want to include can be removed by clicking the small "x" icon which appears upon hover over each category in the drop-zone.
As with categorical subtotals, a subvariable subtotal still appears in bold and can be toggled off and on in the Display Controller.
The subtotal will take the logic of "ORNM" (Or-Non-Missing). Meaning, it will take at least one mention of each subvariable taking all non-missing cases. The non-missing base of the resultant subvariable will therefore be equal to the number of cases where there is at least one non-missing contributing subvariable.
Previously created multiple response variables with subtotals can be edited by returning to the properties panel for that variable and re-entering the Subtotals interface, where you can add new subtotals, delete existing subtotals, or make edits to the subvariables included in subtotals.