How to deal with large 4-gang switch boxes and the need to wire together numerous wires (>4)?
How many wires depends on the nut, and not just the color of the nut. I have red wire nuts that will only take 5 #14 and others that will take 6 #14 (don't recall the #12 numbers off the top of my head and the boxes are not here as I write.) The listed configurations are laid out in detail on the side of the box/container of wirenuts, and you don't get to be creative if a combination is not listed.
Looking on the website of the de-facto standard manufacturer in the US market (no affiliation other than I use them, and pay full price to do so):
Ideal® Wing-nut reds are listed for 5 #12 - their plain Wire-nut reds are listed for 4 #12, the &quot;B-Cap&quot; variant is listed for 5 #12
In any case, if you have more to connect than your particular wire nuts are suited for, divide them up and then add a pigtail between them (which you don't have to count for box fill, but you DO have to count at each end for wire nut capacity.)