> I have following paths added by default to the PATH environement variable.
PATH in Windows must contain only back slashes. Many apps and libraries (C, Java etc) understand and automatically convert / to \ but not in this case.
The STM32 MCU compiler is arm-none-eabi-gcc.exe, there is no need for gcc. There is no need to manually add items to the PATH.
It is all handled internally by the IDE. Are you sure that you have created the correct project type (File > New > STM32 Project)? What is the console output leading to the error shown?