Every text input in train fever does not recognize dead keys to compose accented letter like è é ç ä õ î. Direct input of precomposed characters work though, if they exist on the keyboard or are sent through a system event.

Work around: Since copy and paste won’t work either (as does not coursor navigation) I use a little program called AutoHotkey, which converts my input of [win]+[u] to an [ü]-keystroke.