Press 'R' key once then hold left Ctrl key and press '-' or '+' to Decrease or increase the sim rate Remember the number of presses
you make because...
The first MSFS players on Xbox may be limited to keyboard, mouse and joystick until compatibility with yokes, pedals and throttle quadrants is added...
Xbox Series X is compatible with USB & wireless keyboards and mice and USB Joysticks (with other types of controllers to follow) but the game or app...