Karabiner config for missing backslash keys on US keyboards with Spanish ISO layouts

tilde_backslash.json

{
    "title": "Option+tilde to backslash",
    "rules": [
        {
            "description": "ROption+tilde inserts backslash",
            "manipulators": [
                {
                    "type": "basic",
                    "from": {
                        "modifiers": {
                            "mandatory": [
                                "right_alt"
                            ],
                            "optional": [
                                "caps_lock"
                            ]
                        },
                        "key_code": "grave_accent_and_tilde"
                    },
                    "to": [
                        {
                            "repeat": true,
                            "key_code": "non_us_backslash",
                            "modifiers": [
                                "right_alt"
                            ]
                        }
                    ]
                }
            ]
        },
        {
            "description": "LOption+tilde inserts degree",
            "manipulators": [
                {
                    "type": "basic",
                    "from": {
                        "modifiers": {
                            "mandatory": [
                                "left_alt"
                            ],
                            "optional": [
                                "caps_lock"
                            ]
                        },
                        "key_code": "grave_accent_and_tilde"
                    },
                    "to": [
                        {
                            "repeat": true,
                            "key_code": "non_us_backslash"
                        }
                    ]
                }
            ]
        }
    ]
}