Array of structs inside a struct

Question

Im trying to set a mapping to a struct that contains an array of structs inside. Like so:

struct ParentTokenDetails{
    TokenType _tokenType;
    address _tokenOwner;
    ChildTokenDetails[] children;
}

struct ChildTokenDetails{
    TokenType _tokenType;
    address _tokenOwner;
    bool _locked;
}

mapping(uint256 => ParentTokenDetails) public TokenEnums;

I have a function where I try to do this but so far no luck:

function test()
    public
    returns (uint256)
{
    uint256 newItemId = 1;
    ParentTokenDetails._tokenType = TokenType.NON_FUNGIBLE;
    ParentTokenDetails._tokenOwner = msg.sender;
    ParentTokenDetails.children = ChildTokenDetails([TokenType.NULL, msg.sender, false]);
    TokenEnums[newItemId] = ParentTokenDetails;

    return newItemId;
}

Which prompts the error:

TypeError: Type struct EndLabsEnum.ChildTokenDetails memory is not implicitly convertible to expected type struct EndLabsEnum.ChildTokenDetails storage ref[] storage ref.

Ideally I would be able to create a struct for a new Id with an empty struct array I can add information to later.

Any pointers would help!

Full contract:

//SPDX-License-Identifier:MIT
pragma solidity 0.8.13;

contract TestEnum {
    enum TokenType{ FUNGIBLE, NON_FUNGIBLE, NULL }
    address public owner;

    struct ParentTokenDetails{
        TokenType _tokenType;
        address _tokenOwner;
        ChildTokenDetails[] children;
    }
    struct ChildTokenDetails{
        TokenType _tokenType;
        address _tokenOwner;
        bool _locked;
    }
    mapping(uint256 => ParentTokenDetails) public TokenEnums;

    constructor(){
        owner = msg.sender;
    }

    // Ensure minting of assets with duplicated Ids fail
    function mintNonFungibleTokenEnum(uint256 tokenID)
        public
        returns (uint256)
    {
        uint256 newItemId = 1;
        ParentTokenDetails._tokenType = TokenType.NON_FUNGIBLE;
        ParentTokenDetails._tokenOwner = msg.sender;
        ParentTokenDetails.children = ChildTokenDetails([TokenType.NULL, msg.sender, false]);
        TokenEnums[newItemId] = ParentTokenDetails;

        return newItemId;
}