In Intel® MAX® 10 devices, it is possible to use the CONFIG_SEL pin as a regular I/O pin when the Enable CONFIG_SEL pin option is not enabled.
In Intel® MAX® 10 devices with compact features (feature option SC and DC), the Enable CONFIG_SEL pin option has been removed from Device and Pin Options because these devices don’t support dual configuration image mode.
However, after the removal of this option, the Enable CONFIG_SEL pin option is still being set by default in the Intel® Quartus® Prime Software and you will see the following error message during compilation when assigning an I/O to the CONFIG_SEL pin:
Error (176310): Can't place multiple pins assigned to pin location <pin location> (IOPAD_X<cordinate>_Y<cordinate>_N<number>)
To work around this, add the following assignment into the Quartus Setting File (.qsf):
set_global_assignment -name ENABLE_BOOT_SEL_PIN OFF
This problem is fixed in version 22.1 of the Intel® Quartus® Prime Standard Edition Software.