Multi out option missing : "1/2 + 3/4 + usb5/6" please needed!

Im recording guitar over usb3/4 and vocals over usb5/6, the problem is I can only get to hear the guitar since theres only 1 multi out “1/2+3/4+usb3/4” but for the vocals or any other instrument over usb5/6 or usb 7/8 theres no chance to hear them through headphones or speakers 1/2+3/4 , please ad 1 more multi out “1/2+3/4+usb5/6” and It would be great to also have multi out 1/2+3/4+usb1, 1/2+3/4+usb2, 1/2+3/4+usb3 and 1/2+3/4+usb4, in order to record up to 4 instruments separately and hearing them at the same time. thanks so much!