It is possible. You'll have download another language to be used by the language bar. This would be the easy way out. I think a tilda is easy enough to put on a letter, at least with Finnish keyboards (alt gr+ (the key between enter(return) and ĺ) and then just write the letter on whom you want to put the tilda on) also these ó ň are easy to put on the letters. Also I have letters ö ä ĺ straight on the keyboard. If you want a real shortcut, you'll have to do something trickier, but I can't remember how to map your keys.