Merging multiple array's from a specific class without manually targeting them

Hello, I got into Unity really hardcore, around 8-12 hours a day of continues learning, I just can't stop.

the problem is that I'm trying to merge multiple arrays into one.

I know about System.linq, and about Lists too,

the thing is, that I want to be able to select all of the buttons without manually adding them in-code,

so whenever a new array of buttons is being added, declaring this array/list will add it too.

the class it-self is within a class for customization options, and I can't search them by type as they start in-active in scene, and some spawn in after the scene loads.

I thought about selecting every GameObject within this specific class,

or running a 'for loop' for the length of the class' arrays, and then the arrays themselves for targeting each GameObject, but I couldn't find a way to do so.

This is my code:

     [System.Serializable]
     public class Buttons
     {
         public GameObject[] mainMenuButtons, levelMenuButtons;
         [HideInInspector]
         public GameObject[] levelButtons;
         [HideInInspector]
         public List<GameObject> buttons;
 
         void Start()
         {
             buttons = new List<GameObject>();
             buttons.AddRange(mainMenuButtons);
             buttons.AddRange(levelMenuButtons);
             buttons.AddRange(levelButtons);
         }
     };

Pretty simple code, what's inside the 'Start' function is a temporary solution, and if there isn't any other way it will stay permanent.

So.. is there a way to automate that?

thank you for patience !