gather-and-defend/Assets/Scripts/LevelEditor/TilemapData.cs

using System.Collections.Generic;
using UnityEngine.Tilemaps;
using UnityEngine;
using System;

namespace GatherAndDefend.LevelEditor
{
    [Serializable]
    public class TilemapData
    {
        [SerializeField]
        private string _key;
        [SerializeField]
        private List<TileData> tiles;

        public string Key => _key;

        public void LoadToTilemap(Tilemap reference)
        {
            foreach (TileData data in tiles)
            {
                reference.SetTile(data.Position, data.Tile);
            }
        }
        public void SaveFromTilemap(Tilemap reference)
        {
            _key = reference.name;
            tiles = new List<TileData>();
            BoundsInt bounds = reference.cellBounds;
            for (int i = bounds.xMin; i <= bounds.xMax; i++)
            {
                for (int j = bounds.yMin; j <= bounds.yMax; j++)
                {
                    Vector3Int position = new Vector3Int(i, j);
                    TileBase tile = reference.GetTile(position);
                    if (!tile) continue;
                    var tileData = new TileData(position, tile);
                    tiles.Add(tileData);
                }
            }
        }
        public TilemapData()
        {
            tiles = new List<TileData>();
        }
    }
}