In older versions of WL there was always that “bypass master section” button at the bottom of the window
This would allow you to switch quickly between 2 windows, 1 with the section ON and the other OFF.
Where did this button go? Now all windows seem to share the same setting?
I’m probably overlooking something?
It is still at the same place, it’s the star symbols (one for bypassing master section for that particular audio file or montage, and the other for the sub montage render option and save/load master section in the file.
It still there, it just looks a little different. It’s the smaller of the two stars in the bottom right.
You can also assign a key command shortcut to bypass or activate the master section on the focused montage or audio file. I personally use the shortcut.
ThnX guys! knew I was missing something. 
Note that when per-file Master Section bypass is active, and the file has focus, then the Master Section On/Off button is red.
You can equally click on the bottom right button, or the Master Section On/Off button, to desactivate the file’s Master Section bypass.