Expressions Highlighter

Hi everybody, I don't know if something like this currently exists, but having the ability to highlight expressions would be great for remembering where key lines of code were (like two months later) or if I have to hand off a template file to somebody who doesn't relaly use expressions and tell somebody else, "it's the lines of code highlighted in orange, change x variable". 

Granted, one can always comment, and maybe there's a different approach that's it's equal but having something that would be really nice to have.

As always, thanks for reading.