Tex. Gov't Code § 24.028

If by an amendment to this chapter a county is removed from the composition of an existing judicial district and added to another existing or new judicial district, all cases and proceedings from that county that are pending in the district court of the judicial district from which the county was removed are transferred to the district court of the judicial district to which the county is added. The judge of each affected district court shall sign the proper orders in connection with the transfer.