Hi @Lyra,
From the Navigator schematic (linked to in the Technical Details section of the product page), the Navigator makes use of or exposes all of the Raspberry Pi’s GPIO pins:
Adding extra connections to those pins may be possible in the case where the pins are for a communication protocol with multi-device support, or if you disable the relevant pin(s) from the autopilot’s usage (e.g. like here) if they’re not needed for autopilot peripherals.