Pre-Mute Direct Outputs are not a standard jumper option on the GL2400 mixer.
It would be possible to individually modify each channel to hard-wire the direct output to a pre-mute status,
but this would be a custom-modification which would not be carried out at the factory.
This would need to be carried out by a service centre or a qualified engineer.
We would recommend consulting your local A&H distributor regarding this.
They may be able to advise on a company or individual who may be able to carry out this retro-fit for you.
Please note that modifying the mixer would likely invalidate any warranty remaining on the unit without the express consent of your distributor responsible for the warranty.