If you are looking for them to nest within each other in the inspector, I don’t think the Unity editor supports that. (Someone hop in and correct me if I’m wrong.)
You could make prefabs of each of the types of LevelTowerSystemControllers you want, and then stick those into an array inside of TowerSystemManager. You would just make a blank game object with the LevelTowerSystemController on it, set it up, and save it as a prefab, then drag those four things into TowerSystemManager’s public array.
Yes, I did Grozzier. It is better I explain what I am trying to do. TowerSystemManager has four type of towers in the game(it is a 2d tower defense). LevelTowerSystemController has two upgradable steps of the towers. So, I want the inspector shows up an array called towerType and inside this array another array called towerLevel.
I can see the array tower type on inspector, but I am not able to show the array towerLevel inside the array towerType.
If you are strying to store just values you can use use string and values separated by char like, or / and when need you can read from strings, if you need to drag drop refferences then problem little different.