This is a feature I found REALLY useful in Studio One. Basically just a toggable mono button on the master fader to quickly check mono compatibility. At the moment I am having to open a insert on the master to check, which by the time you have opened/edited/closed way too much mouseclicks than required. It would be also really handy to have the same button situated in the transport panel also. this would make checking mono compatibility a breeze from the arrangement page. even better with a shortcut assigned
I believe it is possible to monitor in mono in the control room but for many people the control room is not a requirement and It would be really nice to have it on the master out.
A very simple but very effective improvement imo