{{ slotProps.option.cname || slotProps.option.name }}
CascadeSelect is used as a controlled component with v-model property along with an options collection. To define the label of a group optionGroupLabel property is needed and also optionGroupChildren is required to define the property that refers to the children of a group. Note that order of the optionGroupChildren matters as it should correspond to the data hierarchy.
{{ slotProps.option.cname || slotProps.option.name }}