There used to be a way in the control panel to disable song requests that would result in a message being sent to chat indicating that song requests have been disabled. Right now there does not appear to be one.
Closing the YouTuble player window disables requests, but no message is sent out, so viewers don’t know until they try and make requests.
This is also a problem for me because I have my overlay setup to show the current playing song from Spotify (using Last.fm data) and when song requests enable I have that logic switch over to reading the current song info from the bot. But since there is no message when song requests are naturally disabled (closing player, etc) my overlay has no event to detect, so it can’t switch back to showing Last.fm data. It used to work great back when the bot announced the status change. Guessing the new panel just missed that.