Finding desabled gameobjects using know positions

So i made a litte js that will make a circle out of blocks. After each one is created is will disable it so i can build 500,000 blocks(cubes) But now i have to have some kind of box or area that i can control with arrow keys to enable them agian, i know each x,y and z position of each block as i make them.

How do i remember them, and how do i make a script that using some kind of area to enable them agian, also need to disable them is my scan has passed it.

I tryed: if (renderer.isVisible){ active = true; } else{ active = false; } But this seems to be hard to test when the Scene camara is also used. It did not work so well.