Not without complication. All transfers to an UTMA account are irrevocable and become the property of the minor. As such, we do not allow self-service requests for delivery of assets from UTMA accounts until they are transferred to the minor.
If you are looking for a vehicle where you can add or remove assets until the assets become part of an estate, consider opening an account in the name of a trust. You should be able to work with an estate planning attorney to create one and easily open an account in its name with HAA (or name it as a beneficiary in your will or other estate documents). Please consult a tax professional about your specific circumstances.