The new Plex experience on Roku no longer has the ability to hide guide. When looking at ghe guide while watching you can no longer simply leave the guide to return to what you are watching. You must either completely exit, and re-enter live tv which takes the usual eternity to re-establish the stream, or go back to the same channel you are watching.
This used to be a very simple process, and it now is extremely painful. There are legitimate reasons, especially during sports season, to just want to take a look at the guide and return to what is being watched.