How do I add a combinator to my style?
You can only add combinators to child selectors. Add a child selector and combinator will appear in the Style tree.
Acquia Cohesion renames to Site Studio from version 6.2. Tell me more.
No, you cannot use SCSS variables in your codebase inside the Acquia Cohesion interface.
To use an SCSS variable, enter your chosen variable into the appropriate CSS property.
Yes, this is possible by creating a custom element.
You don't. You apply a Descendant selector. These use a (Space).
The Youtube video embed is responsive so it should expand to the width of its parent. If you do need to set a width you can apply the Width CSS property through the Style Builder.