how to type diacritical marks using a modifier key?

Hallo KDE List, On my laptop when it was running Windows I could hold down a modifier key to type special accent marks. For example, the right-Alt key and "p" produces the German "oe" (o with two dots over it). How can I do this in KDE/Linux? I've looked at the keyboard language settings, but to no avail. ALt-p produces nothing... :-( -Kevin -- Kevin Pfeiffer International University Bremen