I made a button for my MT New Entry screen to insert special characters via a pop-up window. Let's see if it works, shall we?

¢ £ © ® « » ² ³ ° · < > ~ ∴ ¶ † ¹

Yep it works! Woohoo! I thought the angle brackets might not work as advertised, but it seems fine. Now I just need to add more chars.