If there was something I wanted to adjust or implement, I just inspect the whole core_global_framework.css with ctrl + f keywords. I'm sure down the road IPS will made documentation all the new classes, hopefully. 😁
I played around with a lot of widgets and noticed the text widget had an option to use custom css for the block. I would love to have that feature for all widget, not just text widget 🙂
It took me a hot minute to figure out how to add more css templates that you have to edit the database settings now instead of using the pages management.
Pencil Options for having a "containing database"
Having the pencil options redirecting you back to the selected database settings; or
Removing Pages Includes from the database settings and moving back to page management.