MonoBehaviour execution order from Edit to Play mode and back.

The execution order of event functions in a monobehaviour-derived class is mostly detailed here. Also relevant is this page on execution order settings.

But more to the point, a simple script will allow you to track execution order through the console:

 using UnityEngine;
 
 [ExecuteInEditMode]
 public class ExecutionOrderDisplay : MonoBehaviour 
 {
     private string id;
     
     private string checkMode()
     {
         if(Application.isPlaying)
             return "PlayMode";
         else
             return "EditMode";
     }
     
     void Awake() 
     {
         id = GetInstanceID() + "";
         
         Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::Awake()");    
     }
     
     void OnEnable()
     {
         Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::OnEnable()");
     }
     
     void Start() 
     {
         Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::Start()");
     }
     
     void Update() 
     {
         // enabling the next line clogs the console, obviously
         // Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::Update()");
     }
     
     void OnDisable()
     {
         Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::OnDisable()");
     }
     
     void OnDestroy()
     {
         Debug.Log(checkMode()+"::ExecutionOrderDisplay::"+id+"::"+name+"::OnDestroy()");
     }
 }

Crucially, note the [ExecuteInEditMode] directive, as it is what allows the script to function in both Edit and Play modes. To use the script, simply drag&drop it on an object's components list. In the case of a simple, default cube, it will result in something like this:

On Drag&Drop:

• EditMode: Awake()

• EditMode: OnEnable()

• EditMode: Start()

On Switching to Play Mode:

• EditMode: OnDisable()

• EditMode: OnEnable()

• EditMode: OnDisable()

• EditMode: OnDestroy()

• PlayMode: Awake()

• PlayMode: OnEnable()

• PlayMode: Start()

On Switching back to Edit Mode:

• PlayMode: OnDisable()

• PlayMode: OnDestroy()

• EditMode: Awake()

• EditMode: OnEnable()

• EditMode: Start()

Somewhat interestingly, and maddeningly, is the OnEnable()/OnDisable pair after the first OnDisable() while switching from Edit Mode to Play mode. That's where most of the trouble occurs while trying to come up with custom serialization/file writing functionality. It's unclear why Unity must call that pair instead of simply OnDisable(), OnDestroy() and then entering Play mode. Perhaps is a recompilation step and re-enabling the script catches potential errors? Only speculation at this point as I am not aware of specific documentation on the matter.