Back in 2012 I switched my caps-lock key to act as a second ESC key. This made a big impact in my Vim usage, and you can understand why when you see the keyboard vi was created with.
Having become reliant on that little tweak, it was a little disconcerting to realize that the keyboard layout options I had used to switch my caps-lock were nowhere to be found in Ubuntu 14.04. It turns out that Gnome (upstream from Ubuntu) removed the settings from the system settings entirely.
Fortunately this is still accessible via the Gnome Tweak Tool.
You can install that like this:
sudo apt-get install gnome-tweak-tool
Once installed you can launch the tool from the terminal:
gnome-tweak-tool
You can find the all the old options under the “typing” option.

Its a little weird to have such useful stuff suddenly removed from the system settings. Hopefully they will find there way back in a future version, for the moment, my Vim crisis has been averted and that’s enough.
you don’t need to install anything. Just open dash, type “keyboard”, select “Text entry” and choose the layout you need.
Your comment got me pointed in the right direction; for me it was Dash, Keyboard, Text Entry, Keyboard Settings, Typing, Compose Key, double click on “disabled” to get drop down menu, and then click on option you want to act as your “compose” key. thanks!
Thank you very much, I was desperately looking for a “Layout of numeric keypad” option I used to have on Ubuntu 12.04 : “Obsolete” (haves the point become a coma, the good decimal separator in French). Mattia’s solution doesn’t work when you use a personnal layout…
Will think of you every time I stroke this key!
Thanks! That got my laptop numberbad working!