For example: If you create a new mission, let's say a German one. Yes, the chat and the names support characters like "ä","ö","ü" or "ß" but if I use these characters in a mission file they end up in spaces or question marks on the GUI.

I also tried "&uuml ;" (space between name and ; because this website translates it to a letter...) for a HTML-conform variant of "ü" but that also resulted in "?".

If I understood it right, this is what he means. Simple support for umlauts and other characters while in mission-generation.