The interface for changing the capture key says “Press a function key or key combination to change the capture key.” The former works, but I don’t understand the latter. Am I supposed to be able to do something like press the c and k keys simultaneously and have the Capture Key item become c-k ? Or something analogous? Unfortunately, Apple uses some of the higher-number function keys already (e.g., for Expose) and Mellel uses the lower-level keys for convenient shortcut formatting. I may be able to use F8 without causing trouble with either the Mac or Mellel, but I wonder whether there are other good possibilities to use for the capture key and, if so, how to enter them in the Capture Key field.
P.S., I use a small Alumiinum keyboard; in System Preferences I have clicked the box so that I don’t have to hold down the function key for this type of thing.