Karabiner: Change the backslash key to be delete unless it's held down, then show backslash as normal.

backslash.json

{
  "title": "Backslash to Delete Unless Held",
  "rules": [
    {
      "description": "Change the backslash key to be delete unless it's held down, then show backslash as normal.",
      "manipulators": [
        {
          "from": {
            "key_code": "backslash"
          },
          "to": [
            {
              "key_code": "return_or_enter"
            }
          ],
          "to_if_held_down": [
            {
              "key_code": "backslash"
            }
          ],
          "type": "basic"
        }
      ]
    }
  ]
}