Karabiner complex modification: Post command+backtick if command+escape is pressed. This is useful to those who use 60% compact keyboards on which backtick/grave keys are replaced with the escape key.

karabiner-command-escape.json

{
    "title": "Emit Command+Backtick if Command and Escape are pressed",
    "rules": [
        {
            "description": "Change escape to backtick if pressed with command",
            "manipulators": [
                {
                    "type": "basic",
                    "from": {
                        "key_code": "escape",
                        "modifiers": {
                            "mandatory": [
                                "left_command"
                            ]
                        }
                    },
                    "to": [
                        {
                            "key_code": "grave_accent_and_tilde",
                            "modifiers": [
                                "left_command"
                            ]
                        }
                    ]
                },
                {
                    "type": "basic",
                    "from": {
                        "key_code": "escape",
                        "modifiers": {
                            "mandatory": [
                                "right_command"
                            ]
                        }
                    },
                    "to": [
                        {
                            "key_code": "grave_accent_and_tilde",
                            "modifiers": [
                                "right_command"
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}