Yes, but that switch is not available at runtime. For an Applet it's a constant. By defining "lwjgl_arguments:'-Dorg.lwjgl.opengl.Window.undecorated=true'", the Applet starts with an undecorated window as display. That is undesirable in most cases. It would be better if the user could switch to fake fullscreen and back like a youtube video.
An Applet can already toggle between embedded, window and fullscreen display, but fullscreen is messing up the position of other windows. And there are players who have two monitors and like to be able to see teamspeak / vent / icq / web browser on the second monitor without alt-tabbing back and searching for the windows that have moved offscreen.