Quick instructions:
insert: "keycode 49 = less greater backslash backslash backslash" in "$HOME/.Xmodmap" and run "xmodmap .Xmodmap" - this will setup your keys on the system.
To make these keys persistent run: "xkbcomp $DISPLAY $HOME/.xkbmap"
Very interesting: https://medium.com/@saplos123456/persistent-keyboard-mapping-on-ubuntu-using-xmodmap-cd01ad828fcd
And useful when you want danish keyboard layout with a thai keyboard for instance. I really needed to map backslash "\" to a key on the keyboard because the key does not exist on a thai keyboard when danish keyboard layout is used.
My .Xmodmap file:
Tilde ~ becomes less than "<", greater than ">", and backslash "\":
keycode 49 = less greater backslash backslash backslash
Disable left shift because it is broken and sticks on my T495s, Which is the reason why I will never buy a s series again, because the replacement keyboard is very expensive:
keycode 50 = NoSymbol NoSymbol NoSymbol NoSymbol NoSymbol
So because the left shift is not working I don't use my capslock anymore, and it has become the left shift:
keycode 66 = Shift_L NoSymbol Shift_L NoSymbol Shift_L
Full file content:
keycode 49 = less greater backslash backslash backslash
keycode 50 = NoSymbol NoSymbol NoSymbol NoSymbol NoSymbol
keycode 66 = Shift_L NoSymbol Shift_L NoSymbol Shift_L
NOT in use:
fn button old: keycode 151 = XF86WakeUp NoSymbol XF86WakeUp NoSymbol XF86WakeUp
fn button new: keycode 151 = Shift_L NoSymbol Shift_L NoSymbol Shift_L
keys