Welcome to the QuiltingBoard. If there's no slot on one end, I would use a dremel maybe to remove the rivet at just one end, then you can keep the plate on it. If you have a small enough screw you can use it in the rivet hole for the end you remove.
If you end up removing the entire plate, keep it in a small container of some kind with the machine, so you have the motor specs if you ever need them.