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 obj = this._catDict.get("MarkInfo");
    if (!isDict(obj)) {
      return null;
    }
    const markInfo = Object.assign(Object.create(null), {
      Marked: false,
      UserProperties: false,
      Suspects: false,
    });
    for (const key in markInfo) {
      if (!obj.has(key)) {
        continue;
      }
      const value = obj.get(key);
      if (!isBool(value)) {
        continue;
      }
      markInfo[key] = value;
    }
    return markInfo;
  }
  get structTreeRoot() {