How to toggle on the “Lightmap Static” or any other static type on HDA?
Is it like add unity material to an attribute or something else? thanks.

Make an integer prim attribute with the name “unity_static” and set it to 1

Regards
Bonsak

Here are the docs:
https://www.sidefx.com/docs/unity/_attributes.html [www.sidefx.com]

Is there any way I can set “Scale In Lightmap” in Houdini for Unity?
Also if I set “unity_static” attribute, it just checks all static for me, maybe I just want it to be “Lightmap Static” or something else, how?

We can't really support everything potential option in Unity's components via attributes. Instead, I recommend you add a way to call a custom script that can set that for you. See https://www.sidefx.com/docs/unity/_unity_scripts.html [www.sidefx.com]
The unity_script attribute will add the script component if it doesn't exist on output objects. And it will always call the function specified.

You can also try cook events: https://www.sidefx.com/docs/unity/_assets.html#Assets_AssetInspectorUI_Events [www.sidefx.com]