This is not a secret feature of Sketch, but a standard system-wide macOS OpenType typography panel. (It’s a little buried but it’s available in all apps that use NSTextView.)
I don't think this is a Sketch feature, isn't it the OS font controls?
Don't understand why this was downvoted. Your supposition is right on.
Command + T
Ok am I going crazy or did Sketch used to spellcheck inline years back?
I was hoping this would show me how to maintain superscripts when using Text Styles. Guess not. :(
It even works with text styles. Super handy for monospaced figures etc.
Wow. Why is this so well hidden? Good find.