Saving a button using a file

Note: I'm posting a new answer to completely clarify everything to do with what my answer to the question was_

Description

The only thing you can write to a text file is text. So how can we save a UI element? Well, we can save the state of the button as a string, and interpret that state OnLoad, in order to load the correct button, that was saved.

For example: If we had two types of buttons: 'Buy' and 'Equip', when we are saving our button, we check whether the button is of type 'Buy', or of type 'Equip'. We can save that as a string. Then, when we load our scene, we check the save file for the save state. If the text reads 'Buy', we set the button to a buy button, else if it says 'Equip', we set it to an Equip button. Simple as that.

Example

I re-created a practical example of saving a UI button in the Unity Editor:

Scene View

The scene is comprised of a Main Camera, a canvas with 4 buttons on, and an empty GO, called 'SceneSaver', which has a script on called 'SaveEverything'.

Two of the buttons are the types of buttons you could have in a scene, the Buy and Equip buttons. One of the buttons is called 'MyButton', and is the Button we want to save and load. It has a script on called 'LoadEverything'. The final button is called 'SaveButton' and OnClick, runs a public method called Save() from the SaveEverything script.

Scripts

This is the 'SaveEverything' script:

 using UnityEngine;
 using System.IO;
 
 public class SaveEverything : MonoBehaviour
 {
     // What script to save
     public LoadEverything MyButton;
 
     public void Save()
     {
         // What data to save
         string saveData = MyButton.state.ToString();
 
         // Where the data is stored
         string path = Application.persistentDataPath + "\\buttonstate.save";
 
         // Writes data to file
         if (File.Exists(path))
         {
             File.WriteAllText(path, saveData);
         }
         else
         {
             File.Create(path).Close();
             File.WriteAllText(path, saveData);
         }
     }
 }
 
 public enum ButtonState
 {
     Buy,
     Equip
 }

 

This is the 'LoadEverything' script:

 using UnityEngine;
 using UnityEngine.UI;
 using System.IO;
 using System;
 
 public class LoadEverything : MonoBehaviour
 {
     // Types of buttons
     public GameObject BuyButton;
     public GameObject EquipButton;
 
     public ButtonState state;
 
     void Start()
     {
         // What file to read save data from
         string path = Application.persistentDataPath + "\\buttonstate.save";
 
         // Get data and set state to that data
         if (File.Exists(path))
         {
             string data = File.ReadAllText(path);
             
             if (Enum.TryParse(data, out ButtonState State))
                 state = State;
         }
 
         // Copy button properties onto this button
         // depending on the state
         switch (state)
         {
             case ButtonState.Buy:
                 SetButton(BuyButton);
                 break;
             case ButtonState.Equip:
                 SetButton(EquipButton);
                 break;
         }
     }
 
     void SetButton(GameObject button)
     {
         // Set on-click method of button
         Button myButton = GetComponent<Button>();
         Button targetButton = button.GetComponent<Button>();
 
         myButton.onClick = targetButton.onClick;
 
         // Set text of button
         Text myText = GetComponentInChildren<Text>();
         Text targetText = button.GetComponentInChildren<Text>();
 
         myText.text = targetText.text;
     }
 }

If anything is unclear, let me know. If it doesn't work, let me know. I tested this and it works, so I will help you to re-create my scene. @Ashmit2020