It's good the manual is helping you!
A single H8000 OUTPUT can accept a max. of 2 DSP outputs, so you can collapse a stereo preset to mono in the Routing area of the machine. Collapsing a quad or 5.1 requires Vsig work, adding a mixer to the end of the preset and connect it to a single output. Nevertheless 5.1 presets may not sound good in mono as their whole scope is totally different. Some quad ones may actually sound nice. Trying is the key here….as in most cases.