I'm currently using my AI Modular Matrix Mixer as a pre-mixer of 4 inputs then sent to 2 outputs, so i can send bits of audio to either Monsoon Clouds or Mimeophon, I think this is kind of the arse-backwards way of Effects Sends on a Mixer.
They are also great for mashing up modulation sources.

Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.

https://youtube.com/@wishbonebrewery