FAQ: When should I use selectable key and value?
When you have different variants within the same virtual. For example when you have a sweater that comes in different colors and/or sizes.
If several products share the same virtual_reference, you must use selectable_key and selectable_value.
If there is only one product with a unique virtual_reference, you should not use selectable_key or selectable_value
See video below for examples: