How to rebind AltGr+a to \ with xmodmap?

Question

My keyboard has one less key than my layout, so I have to improvise.

I'd like to bind AltGr+A to backslash "\" instead of "æ", and AltGr+S to pipe "|" instead of "ß". How can I do so using xmodmap (or any other program a user can configure)?

Answer 1

xmodmap -pke lists the configuration of the current layout. I had to add the following lines to my .xmodmap file

keycode 38 = a A a A backslash AE ae
keycode 39 = s S s S bar section ssharp