You can overwrite the file, although I'm not sure that it will let you while the gui is running.
The better option is probably rename the new file keymap.usr and upload it to usr/share/enigma2. Then on the box, menu > info panel > keymap selection and then select keymap.usr. It should then ask you if you want to restart the gui, go ahead and then hopefully it will be working once it has rebooted.
The better option is probably rename the new file keymap.usr and upload it to usr/share/enigma2. Then on the box, menu > info panel > keymap selection and then select keymap.usr. It should then ask you if you want to restart the gui, go ahead and then hopefully it will be working once it has rebooted.