Custom Editor: Array of Structs with elements hidden by toggles

I've got an array of the following struct:

 [System.Serializable] public struct FigureJointControls
 {
     public string name;
 
     public GameObject obj; //the object associated with this joint
     public Vector3 rotation; //the X, Y, adn Z rotations of the joint in degrees
     public bool dependent;
     public int parentIndex; //the index in the list of joint control objects of the parent object
     public float multiplier;
 }

This array is set up in the main function here:

 public class BrachController : MonoBehaviour
 {
     private int tick;
     public int cap;
 
     public int numJoints;
     public FigureJointControls[] primaryJointControls;
     //etc. etc.
 }

I want to display this array in the Inspector and have the bool "dependent" toggle the visibility of "parentIndex" and "multiplier", which are an Int Slider and a float field respectively. Here's what I currently have:

 [CustomEditor(typeof(BrachController))]
 public class BrachScriptEditor : Editor
 {
     override public void OnInspectorGUI()
     {
         var myScript = target as BrachController;
 
         SerializedObject so = new SerializedObject(target);
         SerializedProperty figJoints = so.FindProperty("primaryJointControls");
         
         for (int i = 0; i < myScript.primaryJointControls.Length; i++)
         {
             myScript.primaryJointControls[i].dependent = EditorGUILayout.Toggle("Joint No. " + i.ToString(), myScript.primaryJointControls[i].dependent);
 
             using (var group = new EditorGUILayout.FadeGroupScope(Convert.ToSingle(myScript.primaryJointControls[i].dependent)))
             {
                 if (group.visible == true)
                 {
                     EditorGUI.indentLevel ++;
                     myScript.primaryJointControls[i].parentIndex = EditorGUILayout.IntSlider("Parent Joint Index     ", myScript.primaryJointControls[i].parentIndex, 0, myScript.primaryJointControls.Length);
                     myScript.primaryJointControls[i].multiplier = EditorGUILayout.FloatField("Parent Joint Multiplier", myScript.primaryJointControls[i].multiplier);
                     EditorGUI.indentLevel--;
                 }
             }
         }
     }
 }

This doesn't produce the desired effect. Instead it just shows the toggles but doesn't allow me to edit the length of the array.