How to remap two keys to another combo with two keys

I'm using a Mac Mini running Catalina with a Logitech K270 keyboard, with Karabiner 12.10.0. I've done some simple key changes, I work with latex, where the backslash symbol is written a lot, I get " \ " backslash with AltGr ("right_option") + ("non_us_backslash") keys, I prefer use the combo: AltGr ("right_option") + \ ("grave_accent_and_tilde"). I have in the karabiner.json:

"rules": [
                    {
                        "description": "Barra Invertida",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "non_us_backslash",
                                    "modifiers": "right_option"
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "grave_accent_and_tilde",
                                        "modifiers": "right_option"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    }
                ]
            },

But I can't get the backslash symbol. Any suggestions? Can it be remapped to a single key?