In Settings->Keyboard-Typing I can't change Super+Space to Capslock: it gets ignored, unlike most of the keys. Setting Capslock in Tweak Tool won't work either. What else can I try?
I've submitted a bug: https://bugzilla.gnome.org/show_bug.cgi?id=699541
Other than that, it seems like there isn't much you can do. You can try remapping the caps lock key to something the shortcut editor will accept, but that is hacky.
And it looks like there is a solution! In order to switch to something like Caps Lock or Alt Shift, you need to set the shortcut for "Modifiers-only switch to next source" rather than "Switch to next input source". To set it, you need to press and hold the disable button, mouse over the one you want (Caps Lock), and release the mouse. If this solves your problem, don't forget to mark the thread [SOLVED].
Last edited by UnsolvedCypher (2013-05-03 10:41:15)