Trekkie, when you hit the symbol key on the Pre it will open up a tiny window with all the available special characters that are related to the character you just typed. I doubt that its actually any different if you have german or english language on it.
This is how it looks like on the Pre WebOS emulator set to English when hit SYM + "a"
As you can see, you can access both danish and swedish characters among all the others.
However, it takes some keystrokes to step to a certain character in that list so it would be nice if Palm could somehow rearrange them depending on what country you are in. So that could set it to Danish and have those characters appear first in the list.