When I am in the Device Configuration Tool (MX) and I set ADC1 IN8 Mode to IN8 Single-ended. the IN8 turns orange, and it says "IN8 Conflict with PA4 mapped with GPIO_EXTI4" But IN8 should be mapped to PA3.

[KiptonM]

When I try to set the pin PA3 the choice is ADC1-IN8

And PA4 can be mapped to ADC1-IN9, but I need it GPIO_EXTI4.

This is for the STM32L443CCT

[KnarfB]

Orange is not an error, but just a warning that not every config of that pin/feature is available. In your case: differential mode would not be available, because it needed PA4 as well.

hth

KnarfB