In my opinion the Preset Down switch is the biggest problem the QC has; in particular the way that you need to press the Preset Down footswitch simultaneously with the Tuner footswitch to change Mode is deeply flawed - there ever-present risk of changing Preset by mistake makes this unusable in a live situation, and some people have taken extreme measures to prevent this by using plastic tubing or 3D printed plastic sleeves to lock out the Preset-down footswitch;
Both of these are great solutions, but I think you have to agree that the optics of having to add a $0.50 piece of plastic to a $1500 modeller to make it work better are way off!
There are many calls for a firmware update to allow user customisation of the footswitches overall, and specifically of the Preset Down footswitch.
While I agree that the whole issue of Mode changing/Hybrid mode/secodnary footswitch functions does need to be addressed, in the meantime can I suggest a simple fix?
My suggestion is to add a menu option to allow Preset changing only by a LONG press of the Preset footswitches; the QC does not have gapless Preset changing, so there is never a need to change preset quickly.
Making the Preset change work only by a long press would remove the possibility of pressing the Preset Down a fraction of a second before the Tuner button when trying to change Mode, and accidentally changing preset (which has happened to me when playing live!) and would be a simple a quick fix to address this significant problem.