In Ubuntu 14.10 and prior, I used to go to
gnome-control-center, click Keyboard, and there was some "advanced" section with a list of checkboxes where I could set which key to use as the Compose key. I used the Menu key, but that setting got destroyed with the upgrade, and the Menu key now opens a right-click menu.
However, in Ubuntu 15.04,
gnome-control-center is gone, and when I manually install it using
sudo apt-get install gnome-control-center, it only contains three options: Language Support, Printers, and Software & Updates. No Keyboard section in sight.
As you may have guessed, I'm not using the Unity desktop (but Xmonad). What is the new recommended way to set which key is mapped to Compose?
I'm not averse to editing configuration files, but Ubuntu has a way of breaking unsupported customizations in every new version, so I'd rather do this the "official" way.