Regarding STM32L4Q5CGT6P I wanted to configure PB8 (I2C1 - SCL) and PB9 (I2C1 -SDA) for I2C Bus, but not able to find GPIO PB8 while configurating .IOC in STM32 Cube IDE I am using STM32 Cube IDE version 1.7.0,

[PJang.11]

What is the reason for not finding PB8 pin?

[TDK]

Per the datasheet, that chip (LQFP48 + SMPS) doesn't have PB8 broken out. You'll need to use another chip or another pin.