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The Ctrl+Space keyboard shortcut is really important in Mathematica for using Placeholder[] boxes in input templates. Unfortunately, Ctrl+Space occupies the significantly more important role of the system-wide Quicksilver shortcut that I'm not really willing to part with, not even while Mathematica is running. Can I change this shortcut in Mathematica to some other key sequence?

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Seen this? – J. M. May 6 '13 at 14:40
I'm not sure what you mean by "important for using Placeholder[] boxes". Control-Space is the shortcut for "End Subexpression", e.g. exiting the superscript after pressing Control-6. You can do fine without it. Just use the arrows to exit the superscript. Can you explain what you're doing with Control-Space exactly? I don't understand how it's related to Placeholder[]. – Szabolcs May 6 '13 at 14:40
@Szabolcs: I should clarify: Yes, you can use the arrow keys, but moving out of subexpressions (containing placeholders, hence the reference) using the arrow keys while typing long expressions begins to hurt your wrists after 8+ hours straight or so. – David Hollman May 6 '13 at 14:44
Well, you can always edit and add a different alternate than right-arrow. For my wrists I prefer a single key rather than a combination though. – Szabolcs May 6 '13 at 14:48
I use Windows and use Ctrl+tab to exit subexpressions – Rojo May 6 '13 at 15:08

Thanks to everyone for the helpful comments. Here's the exact procedure I used to fix this (specific to Mac OS X, version 10.8 if that matters, and Mathematica 8, but it should be analogously applicable to other versions and operating systems):

  1. Close Mathematica
  2. Delete the keymap cache. For me this was in ~/Library/Mathematica/FrontEnd/8.0 Caches/MacOSX-x86/SystemFiles/FrontEnd/TextResources/Macintosh
  3. Edit the file. For me this was in /Applications/ For me, the relevant line was 120, reading Item[KeyEvent[" ", Modifiers -> {Control}], "MoveExpressionEnd"],
  4. Reopen Mathematica. The new keyboard shortcut is in place.
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+1 for coming back and describing the solution in detail for everyone's benefit – Szabolcs May 6 '13 at 15:21

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