Hi @CatsNipYummy, welcome to the GLFW forum.
You can use the GLFW Window Hint GLFW_AUTO_ICONIFY to do this. You set this hint with glfwWindowHint prior to window creation, or you can set the similar Window Attribute GLFW_AUTO_ICONIFY using glfwSetWindowAttrib at any point after window creation.
For example:
glfwWindowHint( GLFW_AUTO_ICONIFY, GLFW_FALSE );
// now create window