I’ve checked the nano’s tech specs but I can’t seem to find any information regarding it. I’ve tried setting it to pin 26 (digital output)
The following answer assumes the Arduino is the master.
You can use any pin for that (at least any GPIO pin).
Multiple SPI devices can be connected to a SPI peripheral on an Arduino (in principle).
Every SPI device should have their own CS/CC pin, and is mandatory when you use multiple SPI devices.
For this reason, there is no single pin the SPI can define for being used as CS/CC pin. However, it should give a GND or VCC value, thus a CS/CC pin should typically be configured as a digital input pin (as master) for each slave. (See remark of KIIV too); as slave the CS/CC pin should be a digital output pin.
For the other pins (MOSI, MISO, CLK), the Arduino uses a fixed set of pins because all SPI devices will be connected to these pins.
So the CS pin is configurable, and the other spi pins are fixed.