In Linux/Xorg with a compose/multi-key one can do: <Multi_key> <minus> <minus> <period> : "–" U2013 # EN DASH <Multi_key> <minus> <minus> <minus> : "—"

In Linux/Xorg with a compose/multi-key one can do: <Multi_key> <minus> <minus> <period> : "–" U2013 # EN DASH <Multi_key> <minus> <minus> <minus> : "—" U2014 # EM DASH More in /usr/share/X11/locale/en_US.UTF-8/Compose