1

What I want to do is something like this:

  public GameObject obj1;

    if (obj1 is assigned)
{
  public GameObject obj2;
}

 if (obj2 is assigned)
{
  public GameObject obj3;
}

… and so on…

2

Use an array or List instead. You can’t dynamically add or remove variables.

using System.Collections.Generic;

public class YourClass : MonoBehaviour
{
    public List<GameObject> objs = new List<GameObject>();
}

you can use objs.Add(someGameObject); to add another object to the end of the list. In the inspector in Unity you can simply increase the count to have “more slots”.

3

Don’t you just want:

public GameObject[] obj;

?

4

If you want to INSTANTIATE this game object in the game, you should use instantiate(object, position, rotation) method.

public GameObject[] myObjects;
public int currentObject = 0;

void intantiateObject(){
   GameObject newGameObject = (GameObject)Instantiate(myObjects[currentObject], Vector3.zero, Quaternion.identity);
   // The instantiation will make the game object visible if the object added to the array is active, if don't then you can use:
   newGameObject.SetActive(true);
   currentObject++;
}

If you just want to show and hide them, then use an array reference to the objects.

    public GameObject[] myObjects;
    public int currentObject = 0;
    
    void intantiateObject(){
       myObjects[currentObject].SetActive(true);
       currentObject++;
    }

I hope this help you.