Style Sheets Required Element State

Hello,
I was working through a problem and found a new option I hadn't seen before. Started looking in documentation and trying to find out how to use it. How do you use the Element State Required? and other items?
image

Had you found this?
https://docs.inductiveautomation.com/display/DOC81/How+to+Change+Style+on+Hover

Oops, I don't think it's mentioned there.

Is it to do with a "required" element on a form. e.g., your phone number on a typical web page.

I don't think you can (currently) use required, because it requires your HTML to have a certain attribute, and I don't think any of our first-party components have any configuration to emit that attribute. However, in 8.3.0 we're introducing a new 'form' component where it will probably become more useful.