On Windows 10, Swedish keyboard. When I hit AltGr (right Alt button) and + (which is supposed to give me \), I get nothing in Atom.

After having installed the keyboard-localization package, I now get ~ when I hit this key combo, which is not correct. If I hold down both Alt keys and hit + I get \ with this package installed. However this is not acceptable behavior.

The workaround which worked for me was to uninstall the keyboard-localization package and follow the instructions posted by @csvn here which explains to add the following to the keymap.cson:

'atom-workspace atom-pane':
  'ctrl-alt-=': 'unset!'

To quickly open up keymap.cson from inside of Atom, hit Ctrl+, to enter settings, then choose Keybindings. Click the link in the text to open up keymap.cson.