Sorry ... didn't understand on first glance.
However, after further investigations, I eventually found out some good directions, but I'm still experimenting a little bit and would just like to share first speculations on the matter...

This bug report seems to be of great interest:
https://bugs.maemo.org/show_bug.cgi?id=2892

Virtual Keyboard layouts seem to be stored in:
Fn-Sym Virtual Keyboard: /usr/share/scv_layouts
Closed-Tablet virtual keyboard: /usr/share/keyboards

Here is a dump of a comparison of:
/usr/share/scv_layouts/it.vkb
/usr/share/scv_layouts/us.vkb
with highlighted chars:


Tweaking these files with Hex-Editor, or via tool specified in bug report, might be the way.
Also look at bug report attached XML file:
https://bugs.maemo.org/attachment.cgi?id=713

UPDATE 200912070208v0.1en:
Tried to change some basic values on it.vkb but after reboot, despite file keeps the amended values, no visible changes appear on virtual Fn-Sym Keyboard Layout.
On second attempt, I copied us.vkb to it.vkb and, after reboot, this time italian keyboard layout on screen equals US layout.
It seems that just changing one or more values in the it.vkb file doesn't work!

UPDATE 200912070430v0.2en:
OK... it seems things are starting sorting out
Let's analyze /usr/share/scv_layouts/it.vkb file:


Area surrounded by red line represents values for the normal virtual keyboard buttons. Green line surrounds Shifted virtual keyboard buttons values.
Yellow and Cyan highlights are the values representing the different buttons.
1) Is special code for the TAB button
2) Is the special code for "&" button (the one I needed to implement, both in red and green areas, on the virtual keyboard)
3) Is the special code for "Per Mille" button
4) Are buttons with special characters (~ extended ASCII or UNICODE)

I still haven't figured out the description/meaning for all button values but... so far so good... mission accomplished!!!

... Stay tuned!