Child object of another GameObject invisible or inactive @ runtime

Questions & Answers
1

How do you disable the render or inactivity of the child object of another object?

2

You can set the active state of any GameObject and all of its children with SetActiveRecursively You can also find individual children by name like this and disable their renderer individually with

// make the object invisible
renderer.enabled = false;
3

Parentobject.transform.localScale = new Vector3(0,0,0)

affects all its children without needing to traverse anything and it allows one to have multiple invisibility-chains without the risk of loosing any of them when one is undone.