I would like to inquire about material transmission

Is there a parameter to control the transmittance?
For example this:

material.transmisson = 1.5;

I want to control some parameters to change the effect of casting, but I don’t see it in the documentation.

I think there may be an issue with the terminology or translation of your question. I would re-ask.

Transmission is not a term used, & casting is used for shadows. This does not mean that there is not an answer to your question. As this is a materials question, 2 screen shot illustrating transmission could help.

You can have a look at Mastering PBR Materials | Babylon.js Documentation and translucency