There is the ability to lock the Master fader by holding down the Selection button. But, there is no indicator to let you know that the focus of the Master fader has been locked, nor is there an indication to which mix the fader is locked. As we have multiple users, who may or may not need the fader locked, some sort of indicator is important.
In addition, the documentation related to this feature seems to be missing, or, at best, very difficult to find. It would be very nice to have readily available support documentation detailing the Master fader locking feature and application. For example, one person might be doing the Main mix at the board while a 2nd is using an iPad on stage for monitor mixes. In such a scenario, the iPAD should not steal the Master fader from the Main mix.