[FEATURE] Allow multiple custom keyboard shortcuts

[firefox97]

Problem Statement

For example if you want both Ctrl-W and CtrlF4 to close a tab. I think there are other examples too.
Some internal items already have multiple bindings, so going custom forces only one.

Proposed Solution

Add some way to allow multiple keyboard shortcuts per item. I know it might be a bit hard to figure out a good UI for this, but there are a number of times it would be very nice.

Alternatives Considered

No response

[m1l]

That would require a large rewrite and I am not even sure how to make it. Considering, but low priority because most people will use one. The reason why some functions already have multiples is because Microsoft made a mess so for things like path edit they already have several shortcuts, so to cover situations when someone would know one, and someone else would know some other shortcut