Attention Modified Modifier users! This addon has been rewritten into an entirely new addon!
It's now called ModMod and you can download it here.
This version is being depreciated. It will coexist peacefully with ModMod but the Modified Modifier on this page will no longer be updated.
This addon allows a key (or mouse button) to be bound for use as a fourth "modifier" key for key binding purposes.
For example, if you bind BUTTON5 to be your modifier key (ModMod Key), then bind ModMod+Q to ActionButton 7, then BUTTON5+Q will perform Action Button 7.
__ How to use __
In the default key binding interface near the end is a new binding: Modified Modifier->ModMod Key. This is where you define what your new modifier key will be.
Beside all actions in the key binding interface is a new column of grey buttons where you can bind keys to be used with this modifier.
For as long as the defined ModMod Key is down, the bindings in that new column will perform the action they're bound to.
__ Limitations __
This does not allow the use of the ModMod key to be used as a [mod]ifier in macros.
Nor does this allow the use of the ModMod key to be used for non-ModMod purposes. ie, you can't have Spacebar be your ModMod key and also continue to jump with it.
This does not work with actions not bound through the default key binding interface. That would be up to the addon author who created the custom key binding method.
__ Notes __
I recommend not using this to bind movement keys that start/stop. Releasing the modifier before the bound key will mean you won't stop because it never got the "upstroke" event.
While it's possible to bind ModMod+Left/Right-Click, I don't recommend it because the Turn/Steer can suffer the same issue as above. But it's harmless to experiment if you have a weird setup.
If you really want to bind ModMod+Left-Click, when it asks you to choose a key to bind, click elsewhere (but not a button) in the key binding interface. Left-Click on a button waiting for a bind will cancel the binding change (just like the default buttons).
The ESCape key can't be modified with the ModMod key, sorry.
5/21/2013, 1.0.2, toc update for 5.3
4/20/2013, 1.0.1, initial release