How can i put a master dimmer that will dim all scenes, switches etc. on the master page?

The best way to do that would be create a switch on the master page and turn off ALL the channels for all fixtures except those with a dimmer function. then once your switch is created, click on it then go to buttons> settings> dimmer/ speed, then look for a "show a fader into the button section and check the dot next to "Show the dimmer fader" ok? Let me know if you need help doing any of this.
Sincerely,

I don't think this switch is working.

Did you mean that every channel other than the dimmer channel in every multi-channel fixture should be off (ie. 10 out of 11 channels on every LED bar are off)?

If so, should the dimmer channels be 0%, 100%, or ON (what it says on the top of the strip)?

Should it have a certain priority in settings?

Jingles, please help me out. There's gotta be a way to create a master fader, but I've tried everything I can think of with no results.

hmm kind of yes kind of no. if you use the master page and then open the live toolbar function it gives you a dimmer fader at the top that is used on any scene and all the fixtures linked to master page that have a dimmer. Right click the top of the master page where it says "_MASTER" and select Live toolbar. You should have 3 faders appear. one for dimmer, size, speed. Hope that helps.
Sincerely,