6 band eq level pot.

[Causefarley]

Anyone know what the best way to add a level potentiometer to the 6 band eq knob version?

 

[Cybercow]

You could replace R9 (10K) with an A10K pot, installed rheostat fashion to have a master volume control. It won't get any louder, but it would allow it to be turned down.
The real challenge will be shoe-horning in the extra pot on an already tight build.

 

[Feral Feline]

Install GPCB's AfterBlaster with a 9mm pot, but like the MooMan said, it'll be a tight fit.