The spec for this action:
https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf#G11.2111850
An example of a form using this action:
https://www2.illinois.gov/rev/forms/reg/Documents/reg-1-mr.pdf
const { items } = event.detail;
            while (selectElement.length !== 0) {
              selectElement.remove(0);
            }
            for (const item of items) {
              const { displayValue, exportValue } = item;
              const optionElement = document.createElement("option");
              optionElement.textContent = displayValue;
              optionElement.value = exportValue;
              selectElement.appendChild(optionElement);
            }
            if (selectElement.options.length > 0) {
              selectElement.options[0].selected = true;
            }
            storage.setValue(id, {
              value: getValue(event,  true),
              items: getItems(event),
            });
          },
          indices(event) {