Materials - NitroxNova/humanizer GitHub Wiki
By default, MakeHuman assets will typically have a MHMAT file with associated images, in the downloaded folder. Humanizer will read the mhmat file and generate a material resource from it. You can add additional mhmats in the same folder for different materials.
This process isnt perfect, since mhmats use specular/shininess and godot uses metallic/roughness. If you want to create materials in Godot, create a 'materials' folder in your assets path, create a subdirectory with the asset resource name. You can now create a StandardMaterial3D in this folder, be sure to set the resource name - if you use the same name as an existing material this will override it, useful for retexturing the default materials. and then reload the registry to see your new materials in the authoring dropdowns.