The single biggest most crazy change from T1 to T4S is the burial of the channel 5/6 music input volume controls under several menu manoeuvres in turning the master dial knob>selecting>selecting>selecting rather than the best option as was on the T1 a volume pot at the end of the channel pots.
All very well saying use the volume control on the device or software on the device playing the music but an instant reaction for anyone running a desk in to grab a slider or twist a pot.
Once I have the level set on my device n software to gain an appropriate mix tween music and mic per track I now use the master volume out Plus the mic channel pot to balance for many tracks.
if I turn the overall master out down to drop the music I have to raise the mic channel as that is automatically dropped by lowering the music.
I don’t know of any other “mixer” that operates in the same way.
If I didn’t love the sound so much I’d bin it as the headache it induces constantly having to be near the mic stand to adjust is mind numbing.