Good afternoon.
As I can overlay two textures in the same model.
for example in figure 1 is shown with a texture, and I want to add another texture on top that contains only the texture of the orange line shown in Figure 2.
You don’t seem to be creating a new TextureStage – for each layer of textures, you’ll likely want a new TextureStage.
A simple example, replacing the second piece of code in your post (that is to say, omitting the assignment of the original texture):
newTs = TextureStage("overlay")
tex = loader.loadTexture("textura/imagen2.png")
modelo..setTexture(newTx, tex) # Note that we don't use the third parameter here