What you are suggesting could be done. But I think it comes at a price. Let's say you define the numpad-enter key as the first key in the combination enter-ctrl-F3. In effect you're using it as a modifer key like ctrl, shift, and alt.

Now let's see what happens when you press the numpad-enter key. Normally it generates a "return" keycode. But now HKN has to consider the possibility that you are pressing it only as a modifer for your hotkey combo. In which case you don't want it to generate an "returnr" key code. So surely HKN should swallow the "return" keycode -- in other words, it should disable the key from its normal function.

This is why the "real" modifiers (shift, alt, ctrl) don't generate anything by themselves. If they did, they wouldn't be suitable as modifiers. It seems to me that if you want to use other keys as modifiers, certainly that could be done, but like the real modifiers, they have to be disabled from generating anything by themselves.

This wouldn't be hard to implement. But I chose not to (so far at least) because I thought most people would find it confusing. I imagined them writing a single hotkey defintion with some "normal" key as a modifier. Then they load the definition, and suddenly they key is disabled except when it's used to trigger that hotkey. Then they get mad at the program and remove it from their hard disk.