For Wisconsin (and Illinois) the statute is "A trust created by a decedent's will (testamentary trust) is resident at the domicile of the decedent at the time of the decedent's death, unless transferred by a court having jurisdiction to another court's jurisdiction."

I had a similar situation where the decedent died in FL, beneficiary moved to WI and transferred the executor power to her son in Illinois. The irrevocable trust remained a resident of FL per the family's Trust attorney.