This is not currently possible, but I can log your feature request.
When using 2 presets in parallel on the H90, you can have Inputs 1-2 processed by Preset A, and 3-4 processed by Preset B, or vice versa. This will be determined by where your stereo insert is placed in the path; place it before Preset A and inputs 3-4 will be processed by Preset A, while inputs 1-2 are only processed by Preset B.
