Basically, the functionality I found is that when adding a model and not defining material, the materials used have two sides.

I guess of course because of using the properties from the glTF ("doubleSided": true)-

Creating materials in Plume remove that property somehow.

In my opinion it is always advisable to have 3d mesh for the areas meant to be visible, not trust the double side materials. But in some cases, for example specific models that would use "embedded" materials from the glTF plus Plume defined materials, it would save a lot of time in the modeling area to be able to display those Plume defined materials as two sided.

And at the end it is about how it looks like in the 3d canvas. The final user would not know if something is modeled or not.

Additionally, it could improve performance too at least regarding loading times and maybe calculations too? (Less mesh, less vertices, less files size).

So, would it be possible to have the DoubleSided option in the material definition?