To do that you would probably have to edit the cutscene_camera_follow_object script.
I can’t test it right now, but maybe this can help: https://forum.gamemaker.io/index.php?threads/how-to-make-an-object-smoothly-change-position.108897/
Or maybe another option could be to use cutscene_camera_moveto_position to move close to the door and then use cutscene_camera_follow_object with a different speed?