Seems like there there is no solution due to technical limitation, only
changing/creating new component, we have opened a ticket with Adobe and
this is the reply we have got:"The behavior you are witnessing is an
expected behavior.It is not recommended to use the multi-field for the
product scaffolding as creating sub nodes for product attributes is
orthogonal to the expected product data structure. Products attributes
should be stored directly at the product or variant node. Child nodes
ideally...