Using Keil UV3 V3.85 I can use peripheral > SPI > SPI_2 to show register details, how do I display I2S_2, I2S_3 peripherals in a similar way ?
Since I2S isn't listed as simulated, it isn't just the GUI that is missing. Without any simulation, there will not be any raw registers to access. Maybe mixup between I2S and I2C - I2C1 and I2C2 are simulated.
Sorry, yes; that's true - I was just thinking of the debugger accessing the real registers on the real hardware.