Hello,
I have used xbindkeys for my shortcuts for a long time, but I want to try to use kde's shortcuts instead.
I have two issues so far.
1) The only modifiers I can have are ctrl, alt and shift. With xbindkeys, I can use X's modifiers, defined with xmodmap. (shift, caps lock, ctrl, mod1...mod5). Three modifiers instead of eight just isn't enough, and I can't figure out how to change that.
2) Not as important, but it would be really nice if I could import my xbindkeys shortcuts into kde's shortcut system.

Any help is appreciated!

(edit) Actually, I didn't notice meta worked, but it still isn't enough...

A solution would be 2-times shortcuts, like those used to unlock/add widgets, but I can't find how to do that. I can't even find where you can modify these shortcuts.

At the same time it would be really nice to know how to identify which shortcut keys are currently reserved by KDE or any other program. Is there some way to find this out (a kde program, a file stored somewhere, etc)?

There are files in ~/.kde/share/config with the shortcuts. Actually, you have a lot of files in it.
You have your global bindings in kglobalshortcutsrc.
You have the custom stuff in khotkeysrc. (including mouse gestures)

But I couldn't find the bindings of the desktop (i.e. lock/unlock widgets), nor the standard shortcuts, used by all applications.

So I think I'll give up about this, since xbindkeys is much more flexible, regarding the shortcuts (more modifiers, and it allows sequences of keystrokes) and the portability (only one file to copy, nothing to rewrite if you wrote your commands right in the first place).

Unless you have changed them, then some of the shortcuts (those set by applications at least) will be stored in the system wide KDE installation path (usually under /usr)