You may be able to formalize your agreement under the laws of the nation in which you divorced. In some divorces it is necessary to bring an ancillary proceeding to address the division of property in another jurisdiction, but that's normally only necessary for titled property where the parties to the divorce cannot agree and cooperate on its division.

If you and your ex- are in agreement, it makes sense to expeditiously carry out the agreement such that it is no longer an issue. You should be able to close joint accounts and transfer vehicle titles over a short amount of time.