xmodmap, a combination which does not use Mode_switch

[Eugen Dedu <eugen.dedu@univ-fcomte.fr>]

Hi,

I do not succeed in mapping the Home "key" to a given combination.

I have already mapped in my .xmodmap file:
! set AltGr as Mode_switch
keycode 108 = Mode_switch
and it works well to type accentuated characters for example.

I have recently changed my laptop.  On it (Dell), the Home key is on the 
first line of the keyboard (right of Fn keys), which I found to be too 
far for my fingers, and too distant compared to arrow keys.  So I want 
to map Home to a key at the bottom of the keyboard.

Unfortunately, the combination Fn + left arrow does not have a scancode, 
this combination does not give any code in xev and showkey, so I cannot 
use it.

Therefore, I want to set Home key as mod4 (windows key) and left arrow.

I spent already a lot of time to find out a solution for my problem, 
without success so far.  All the methods found in Internet use 
Mod_switch, but in my case Mode_switch is already set to another key, as 
written above.  Can I map mod4 and left arrow to Home without using 
Mode_switch?

Best regards,
Eugen