As far as I know, the only correct answer to your question is "modify Firefox's program files."

And yet I am certain that is not helpful.

What's wrong with Firefox's built-in keyboard shortcuts? (Keyboard shortcuts - Perform common Firefox tasks quickly)

And what's wrong with using add-ons to change them?

I actually made this happen a few versions back, but I don't remember how I did it. I have looked through the about:config entries and can't find it. I looked through the ...xul keybindings and did not find it. I know it can (or recently could) be done, but I don't remember how.

The problem with the existing shortcut is that on a laptop, the Home button is frequently sharing space with another key. It is a hassle to have to access Home and the alt key when accessing Home is itself an operation.

The problem with add-ons is that I cannot, in a reasonably quick momentary glance, determine their safety now, nor in the future as they are updated. Since Mozilla does not certify add-ons as safe, I prefer to avoid them.

Other programs don't present such difficulties with simple things like modifying shortcuts. It's pretty standard for that to be accessible from a Customize submenu in one of the main drop-downs.

I share your concern about trusting add-ons; you don't know.

In the following thread we discussed files to hack: Making the Home/End keys work on Mac like they do on Windows/Linux.