The court may order the separate trial of the principal and incidental actions, either on exceptions or on the merits; and after adjudicating the action first tried, shall retain jurisdiction for the adjudication of the other.

When the principal and incidental actions are tried separately, the court may render and sign separate judgments thereon. When in the interests of justice, the court may withhold the signing of the judgment on the action first tried until the signing of the judgment on the other.