The values are stored in ~/.config/dconf/user but this is a binary and not human readable so I don't know how you would edit it.
You can view it with
xxd ~/.config/dconf/user
Source0
Source1
As requested here is a .desktop file that will run gsettings set org.gnome.desktop.background show-desktop-icons true on boot
Open a new document in a text editor and paste this in
[Desktop Entry]
Type=Application
Exec= gsettings set org.gnome.desktop.background show-desktop-icons true
X-Gnome-Auto-Start=True
Name[en_GB]=icons.desktop
Save it as icons.desktop and make it executable by right click or
chmod +x path/to/icons.desktop
Now double click icons.desktop to confirm it works.
Once you are happy it works move it to ~/.config/autostart, if it does not exist, make it
mkdir ~/.config/autostart
Now when you reboot, this will run and activate the icons, if they are already active, it will just do nothing.