I mean you can overwrite the Tameriel LOD meshes from the first time generation with renamed markarth terrain meshes(with Markarth LOD unlocked disabled) from the second time generation. This method is just a workaround so I will try the method you mentioned here and see if the issue still persist. Thanks for your reply.
So in order to fix the Cidhna Mine Terrain Issue, the best practice would be running xlodgen twice, the first time generate all worldspaces except for markarth world then generate only markarth world for the second time, right?