there has been a request in the forum for a mixer module specifically, so maybe that is something I will end up doing.
The VCA module, which can take care of normal VCA duties and can be a building block for mixers, was requested by people in the forum partly to deal with building mixing flows.
There is also the macro module and macro page at the global level. With macros you can control multiple things in the patcher grid from one location (the global page), so if you build VCAs/mixer modules into your patch you can control them from there. Or you can use the MIDI module with a MIDI controller to control stuff in the patch.
The SSP has 16 inputs so you could also use a CV fader bank as a mixer, together with the VCA(s) you put in the SSP’s patcher grid.