This post is long, somewhat hard to explain and I'm only on my first cup of coffee so bear with me...
You only have 8 buttons you can assign per preset, but you can assign them to anything. You technically have 11, but I have the 3 function buttons set to preset up, preset down and tuner.
Assuming one button per channel module, you would not be able to have a preset containing all 8 channels and have any way to directly footswitch effects on and off. That does not mean you cannot add 8 effects to the preset, just that you wouldn't be able to footswitch them easily.
You get around this limitation by using scenes. Here's what I do:
I create a preset for a specific song in our setlist. I decide which effects I will be using on that song and I add all of them to the preset. Then I decide which module channels I will be using for that song and I create scenes inside the preset corresponding to the module channels.
Effects are assignable per preset, but you cannot add new ones to different scenes inside the preset. But you CAN toggle them on and off, or X/Y them. So while you can't change what effects you use in a scene, you can change their state (on/off, or 2 different settings via X/Y)
So for example, let's say we sometimes play a song that calls for a clean channel, crunch channel and a lead channel. It has delay, reverb, phaser and a harmonizer and wah.
I create a preset with all those effects I will be using on the song, then create several scenes inside it, with the effects in various states.
Wah is assigned to the expression pedal so it is always available. Just have to step on it.
Scene 1 is set to a clean module channel, with phaser, delay and reverb on, and harmonizer off. I assign this to button 1.
Scene 2 is a crunch channel on a different module, with just delay and reverb on, phaser and harmonizer off. I assign this to button 2.
Scene 3 is lead tone on channel B of the second module, with delay, reverb and harmonizer on, with phaser set to off. I assign this to footswitch button 3.
This leaves me with 5 buttons to assign. I generally put a gate on one button, so that I can turn it on and off as needed. I also put as many fx as I can on the remaining buttons so that I can toggle them on and off as needed. This is dependent on how many scenes you have for that song (you can create 8 inside of every preset).
So when it's all said and done, my 8 footswitches for this one preset are as follows:
1 - scene 1 (delay/reverb/phaser on, harmonizer off, MIDI PC 1)
2 - scene 2 (delay/reverb on, phaser/harmonizer off, MIDI PC 3)
3 - scene 3 (delay/reverb/harmonizer on, phaser off, MIDI PC 4)
4 - phaser
5 - gate
6 - harmonizer
7 - delay
8 - reverb
So if I'm playing scene 1 and I decide I don't like the phaser sound, I can step on button 4 and turn it off and the scene stays active until I change to another one.
I do also have a "default" preset I use for goofing around with all my modules. The scenes in it are set 1-8 to each footswitch so that I can switch to every channel in a single preset. This has delay and reverb on for all 8 along with the wah, so the only difference is each scene channel switches.
Confusing, but once you set this up one time it will make total sense. You just have to adjust your approach a little. It's very much like using a loop strip. One button press toggles certain things on and off.