Update

Assets/D.A. Assets/DA-Shared/Editor/DAInspector/InfinityScrollRectWindow.cs

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+using System.Collections.Generic;
+using System.Linq;
+using UnityEditor;
+using UnityEngine;
+
+namespace DA_Assets.DAI
+{
+    public delegate void DrawItem<T>(T item);
+
+    public class InfinityScrollRectWindow<T, T4> where T4 : CustomInspector<T4>, ICustomInspector
+    {
+        public DAInspector gui => CustomInspector<T4>.Instance.Inspector;
+
+        private T[] _items;
+        private Vector2 _scrollPosition;
+        protected int _visibleItemCount;
+        protected float _itemHeight;
+        private float _totalScrollHeight;
+        private float _visibleAreaHeight;
+        private DrawItem<T> _drawItem;
+
+        public InfinityScrollRectWindow(int visibleItemCount, float itemHeight)
+        {
+            _visibleItemCount = visibleItemCount;
+            _itemHeight = itemHeight;
+        }
+
+        public void SetData(IEnumerable<T> items, DrawItem<T> drawItem)
+        {
+            _drawItem = drawItem;
+            _items = items.ToArray();
+
+            if (_items.Length < _visibleItemCount)
+            {
+                _visibleItemCount = _items.Length;
+            }
+
+            _visibleAreaHeight = _visibleItemCount * _itemHeight;
+            _totalScrollHeight = _items.Length * _itemHeight;
+        }
+
+        public void OnGUI()
+        {
+            if (_items == null || _items.Length < 1)
+            {
+                GUILayout.Label("No data.");
+                return;
+            }
+
+            if (_drawItem == null)
+            {
+                GUILayout.Label("DrawItem is missing.");
+                return;
+            }
+
+            gui.Colorize(() =>
+            {
+                _scrollPosition = EditorGUILayout.BeginScrollView(_scrollPosition, GUILayout.Height(_visibleAreaHeight));
+            });
+
+            float currentScrollPos = _scrollPosition.y;
+            int startIndex = Mathf.Max(0, (int)(currentScrollPos / _itemHeight) - 1);
+            int endIndex = Mathf.Min(_items.Length, startIndex + _visibleItemCount + 2);
+
+            GUILayout.BeginVertical();
+            GUILayout.Space(startIndex * _itemHeight);
+
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                _drawItem(_items[i]);
+            }
+
+            GUILayout.Space(_totalScrollHeight - endIndex * _itemHeight);
+            GUILayout.EndVertical();
+
+            EditorGUILayout.EndScrollView();
+        }
+    }
+}