Two Customizable Shortcuts for Each Action?

[helvib]

Here is a tentative suggestion: To allow for two customizable shortcuts for each event/action.

We have seen this feature in games and it could seem superfluous here. But sometimes, it's helpful, as in the case of the horizontal scroll: We could have two shortcuts: Shift+Scroll, and Lef/Right cursor keys.

There more power the user feels over the software, the more s/he will like it.

[Ivan - Tracker Software]

To be honest customizing even one shortcut makes for us a lot of trouble and introduces some limitations.
Just one example:

add bookmark command has different behaviour depending which key (Shift, Ctrl or both) is pressed during execution of this command.

Now please imagine somebody will make shortcut for this command with one (or both) of these keys? What to do - make a lot of workarrounds or remove functionality ?