How to find certain TextMeshProUGUI if multiple are attached?

I have an inventory with six slots. Each slot has three TextMeshProUGUI attached: singleGoldAmount, stackSize, resultingGoldAmount. These TextMeshProUGUI are tagged with names corresponding to their purpose.

I want the inventory in Start() to find each TextMeshProUGUI-Element and put them in a list like private TextMeshProUGUI [] singleGoldAmountText, vice versa for stacksize and resultingGoldAmount. I've tried FindWithTag, but didn't get the solution I was looking for.

I've tried to solve this for two days but I feel like I'm not making any progress. By now, I'm probably blind to the obvious solution and too stupid to abstract from this particular problem.

This is as far as I came: using System.Collections.Generic; using System.Collections; using UnityEngine; using System; using TMPro; using UnityEngine.Serialization;

 public class Inventory : ItemContainer
 {
     [SerializeField] List<Item> startingItems;
     [SerializeField] Transform itemsParent;
 
     // Blubb testing stuff here
     [SerializeField] List<Werkstatt_Slot> werkstattSlot;
     [SerializeField] Transform werkstattSlotTrans;
     // Blubb ending testing
 
 
 
     public string Goldwert;
 
     
     public void Start() 
     {
         SetStartingItems();
         Init();
     }
 
     private void Init()
     {
         for (int i = 0; i < werkstattSlot.Count; i++)
         {
             // ?? I'm fairly sure I need this to fill the list?
         }
     }
 
     private void OnValidate () 
     {
         // GoldWertFeld = TextMeshProUGUI.FindGameObjectsWithTag("Goldwert"); // NOPE NOT WORKING
         if (itemsParent != null)
         {
             itemSlots = itemsParent.GetComponentsInChildren<ItemSlot>(); //Works like a charm
             werkstattSlot = werkstattSlot.GetComponentsInChildren<Werkstatt_Slot>(); //Does not work
             // itemWert = itemsParent.GetComponentsInChildren<TextMeshProUGUI>(); //Works, but only as long as there is only ONE type of TextMeshProUGUI... I have three now.
             // itemWert = werkstattSlotGO.FindWithTag("Goldwert").GetComponentsInChildren<TextMeshProUGUI>(); //This was another try. Didn't work.
             //    itemWert = GameObject.FindWithTag("Goldwert").GetComponentsInChildren<TextMeshProUGUI>(); // This one finds a single entry. 
 
             // itemWert = GoldWertFeld.GetComponent<TextMeshProUGUI>(); // Nope
         }
 
         SetStartingItems();
         Init();
     }
 
 
     private void SetStartingItems()
     {
         int i = 0;
         for (; i < startingItems.Count && i<itemSlots.Length; i++)
         {
             itemSlots[i].Item = startingItems[i].GetCopy();
         }
 
         for (; i<itemSlots.Length; i++)
         {
             itemSlots[i].Item = null;
         }
     }    
 }

Could somebody help me out? Pointing me to a tutorial would be fine, too, I am just really stuck in a circle here.