Do not combine them unless your model's instructions explicitly call for that arrangement. An automatic dose plus a separate ordinary dose can give the laundry more detergent than intended.
Understanding this situation
Some machines provide a manual compartment for a special product while allowing the automatic system to be disabled for that cycle. Others use different controls or rules. The important step is identifying which system will actually dispense on the selected programme, rather than assuming the drawer can distinguish your intention from what you poured in.
A useful next step
Check the dosing indicator and relevant programme instructions before adding product. For a one-off delicate or specialist wash, follow the documented method of selecting manual dosing. If sudden foaming began after you added both products, explain that sequence honestly; it is more helpful than reporting foam without mentioning the extra detergent.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.