You may know this and it isn’t a per preset function but …
H90 Release 1.8.5
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Force Mono
Override jack-detection and output mono even when wired for stereo
Useful for patchbay setups or switching between mono & stereo rigs
Preserves stereo information as long as possible through H90 effects and inserts for all routing configurations
Found under System > I/O > Output Mode
