Saving Non-Prefab Data During Editor Play

I've been looking into how I could save specific changes made to non-prefab data from Editor Play sessions (Unity version 4.7). I thought I had my head around it, but that doesn't seem to be the case. Below I've got a serialized struct and a serialized field from another class where I use a List of those structs. It works for saving data from Editor->Play, but not the other way around:

 [System.Serializable]
 public struct AdditionalNodeData {
     
     public AdditionalNodeData (int indexOfNode, uint tagValue)
     {
         nodeIndex = indexOfNode;
         nodeTagValue = tagValue;
     }
     
     public int nodeIndex; //coming from each node in the navmesh.
     public uint nodeTagValue; //filled with the node tag as it first appears in the scene (determined and saved during Editor creation).
     
     //public bool isClaimed = false; //has this node already been used to restore information.
 }
 
 
 //other class script
     [SerializeField]
     private List<AdditionalNodeData> andL = new List<AdditionalNodeData>(); //a struct containing node data as it was in a 'clean state' before modification.
     public List<AdditionalNodeData> Andl { set{andL = value;} get{return andL;} } 

I know I could save some data out as a scriptable object (and maybe I will), but for now its faster to just copy/paste the data from the Play session out to the script after I'm done.

So, there is obviously a way to do it, but I'm still not sure I understand what it is. Any clarification / pointer to the proper reading material is appreciated.