The language in the Arduino IDE is C/C++. It all gets fed into a C/C++ compiler at the end. In the Arduino IDE, you just don’t have to write
#include <Arduino.h> and function prototypes, all of which is documented online.
You need to have a more specific question than “how do I get platformio to behave this way”, describing what “this way” is (a specific error you encountered?), what you want improved and also use friendlier language.