Your comments

I think something similar to this would be awesome!
Another way to do it would be to select / highlight some rows, press like ctrl+alt+H or some shortkey, and that stay's syntax colored but the rest, outside, is faded / grayed out.

Multi-highlight would be great, if you're working in two different sections / methods or so, so if you start typing at another line that segment should also get highlighted.

Hope some hacky figure would see this as an interesting feature to develop! :D

Regards, Pierre