Hey there,
I found to some degree it is possible to work with material stacking with corona if you enable "Add Material" in the material tag and add any texture as diffuse texture.
Thing is Corona Renderer seems to be interpreting the "Add Material" Mode in the wrong way which makes it display incorrectly.
Attached you can see 2 comparisons of stacked materials. First row with a green checkerboard texture, second row with a solid green color. Corona seems to be falsely multiplying the Diffuse texture with the Material underneath instead of overlaying it on top like the standard C4D Materials do. This is a thing that should be fixed.
The material underneath turning black otherwise is probably because you did not turn on "add material"(?).