Adding support for CSS Custom properties and CSS Grids

Hi
I’m reading a lot about these 2 modern concepts. Well, I think if working with IE11 in mind they could be ready to be used.

Is Sage 9 ready for them? I mean:

So, what I have to set in Sage 9 to make use of them?

Any advice is appreciated
Thanks

Someone could help me to understand how to implement postcss-custom-properties in Sage 9?

This not worked for me How to set up Sage with postcss custom properties?

Thanks