Neo

Neo is a Craft CMS field type that builds upon the concept of the Matrix field type with a number of very useful features. Neo has been carefully crafted (pun intended) to ensure it matches the look and feel of Craft.

Since the Neo field is referencing other fields it should be at the bottom of your fields list.

{
    "fields": [{
        "group": "Default",
        "name": "Neo Test",
        "handle": "neoTest",
        "instructions": "This is not a required field.",
        "type": "Neo",
        "typesettings": {
            "maxBlocks": 3,
            "groups": {
                // The order of these are important. Group A will match with sortOrder 2 and Group B with 4
                "name": [
                    "Group A",
                    "Group B"
                ],
                "sortOrder": [
                    2,
                    4
                ]
            },
            "blockTypes": {
                "new0": {
                    "sortOrder": "1",
                    "name": "Block A",
                    "handle": "blockA",
                    "maxBlocks": "",
                    "childBlocks": ["blockB"],
                    "maxChildBlocks": 5, // Required if no maxChildBlock use empty String. Affects v1.5.5.1 and later. Not required in v1.5.5.2 and later
                    "topLevel": "1",
                    "fieldLayout": {
                        "Tab 1": [
                            "handleOne",
                            "handleTwo"
                        ],
                        "Tab 2": [
                            "handleThree",
                            "handleFour",
                            "handleFive"
                        ]
                    }
                },
                "new1": {
                    "sortOrder": "3",
                    "name": "Block B",
                    "handle": "blockB",
                    "maxBlocks": "",
                    "childBlocks": [],
                    "maxChildBlocks": "", // Required if no maxChildBlock use empty String. Affects v1.5.5.1 and later. Not required in v1.5.5.2 and later
                    "topLevel": "",
                    "fieldLayout": {
                        "Tab 1": [
                            "handleOne",
                            "handleSix",
                            "handleEight",
                            "handleTwo"
                        ]
                    }
                }
            }
        }
    }]
}