I'm using this to set the cursor on the center of the screen to be able to pan the view around using mouse input like any other 3d game:
glfwSetCursorPos(WINDOW, Main.WIDTH/2, Main.HEIGHT/2);
It is working, but I want to add a crosshair. A simple GUI image centered. I want to keep the mouse functionality, but to hide it and keep only the crosshair.

Sorry. I just found the solution:
glfwSetInputMode(WINDOW, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);