diff --git a/Source/Editor/Content/Proxy/JsonAssetProxy.cs b/Source/Editor/Content/Proxy/JsonAssetProxy.cs
index 27d0e2347..dfdec8330 100644
--- a/Source/Editor/Content/Proxy/JsonAssetProxy.cs
+++ b/Source/Editor/Content/Proxy/JsonAssetProxy.cs
@@ -1,9 +1,11 @@
 // Copyright (c) 2012-2024 Wojciech Figat. All rights reserved.
 
 using System;
+using System.Linq;
 using FlaxEditor.Content.Create;
 using FlaxEditor.CustomEditors;
 using FlaxEditor.CustomEditors.Editors;
+using FlaxEditor.Scripting;
 using FlaxEditor.Windows;
 using FlaxEditor.Windows.Assets;
 using FlaxEngine;
@@ -84,18 +86,67 @@ namespace FlaxEditor.Content
 
                     if (_element != null)
                     {
-                        // Define the rule for the types that can be used to create a json data asset
-                        _element.CustomControl.CheckValid += type =>
-                        type.Type != null &&
-                        type.IsClass &&
-                        type.Type.IsVisible &&
-                        !type.IsAbstract &&
-                        !type.IsGenericType &&
-                        type.Type.GetConstructor(Type.EmptyTypes) != null &&
-                        !typeof(FlaxEngine.GUI.Control).IsAssignableFrom(type.Type) &&
-                        !typeof(FlaxEngine.Object).IsAssignableFrom(type.Type);
+                        _element.CustomControl.CheckValid += OnCheckValidJsonAssetType;
                     }
                 }
+
+                private static Type[] BlacklistedClasses =
+                [
+                    typeof(System.Attribute),
+                    typeof(FlaxEngine.Object),
+                    typeof(FlaxEngine.GUI.Control),
+                ];
+
+                private static Type[] BlacklistedStructs =
+                [
+                    typeof(Float2),
+                    typeof(Float3),
+                    typeof(Float4),
+                    typeof(Double2),
+                    typeof(Double3),
+                    typeof(Double4),
+                    typeof(Vector2),
+                    typeof(Vector3),
+                    typeof(Vector4),
+                    typeof(Half2),
+                    typeof(Half3),
+                    typeof(Half4),
+                    typeof(Int2),
+                    typeof(Int3),
+                    typeof(Int4),
+                    typeof(Transform),
+                    typeof(Quaternion),
+                    typeof(BoundingBox),
+                    typeof(BoundingSphere),
+                    typeof(BoundingFrustum),
+                    typeof(Ray),
+                    typeof(Plane),
+                    typeof(Matrix),
+                    typeof(Color),
+                    typeof(Color32),
+                    typeof(FloatR11G11B10),
+                    typeof(FloatR10G10B10A2),
+                    typeof(FlaxEngine.Half),
+                ];
+
+                private static bool OnCheckValidJsonAssetType(ScriptType type)
+                {
+                    // Define the rule for the types that can be used to create a json data asset
+                    var mType = type.Type;
+                    if (mType == null ||
+                        type.IsAbstract ||
+                        type.IsStatic ||
+                        type.IsGenericType ||
+                        !mType.IsVisible)
+                        return false;
+                    if (type.IsClass)
+                        return mType.GetConstructor(Type.EmptyTypes) != null && BlacklistedClasses.FirstOrDefault(x => x.IsAssignableFrom(mType)) == null;
+                    if (type.IsStructure)
+                        return !type.IsPrimitive && 
+                               !type.IsVoid && 
+                               !BlacklistedStructs.Contains(mType);
+                    return false;
+                }
             }
         }
 
@@ -175,7 +226,7 @@ namespace FlaxEditor.Content
         {
             _thumbnail = SpriteHandle.Invalid;
         }
-        
+
         /// <summary>
         /// Constructor with overriden thumbnail.
         /// </summary>
@@ -196,7 +247,7 @@ namespace FlaxEditor.Content
         {
             Editor.SaveJsonAsset(outputPath, new T());
         }
-        
+
         /// <inheritdoc />
         public override AssetItem ConstructItem(string path, string typeName, ref Guid id)
         {
diff --git a/Source/Editor/GUI/Popups/TypeSearchPopup.cs b/Source/Editor/GUI/Popups/TypeSearchPopup.cs
index d3407eda2..cb731a0df 100644
--- a/Source/Editor/GUI/Popups/TypeSearchPopup.cs
+++ b/Source/Editor/GUI/Popups/TypeSearchPopup.cs
@@ -1,10 +1,13 @@
 // Copyright (c) 2012-2024 Wojciech Figat. All rights reserved.
 
 using System;
+using System.ComponentModel;
 using System.Linq;
+using FlaxEditor.History;
 using FlaxEditor.Scripting;
 using FlaxEngine;
 using FlaxEngine.GUI;
+using CategoryAttribute = FlaxEngine.CategoryAttribute;
 
 namespace FlaxEditor.GUI
 {
@@ -101,11 +104,26 @@ namespace FlaxEditor.GUI
                 if (_isValid(type))
                 {
                     var attributes = type.GetAttributes(true);
-                    if (attributes.FirstOrDefault(x => x is HideInEditorAttribute || x is System.Runtime.CompilerServices.CompilerGeneratedAttribute) == null)
+                    if (IsHideAttributes(attributes))
                     {
                         var mType = type.Type;
-                        if (mType != null && mType.IsValueType && mType.ReflectedType != null && string.Equals(mType.ReflectedType.Name, "<PrivateImplementationDetails>", StringComparison.Ordinal))
-                            continue;
+                        if (mType != null)
+                        {
+                            // Skip if type is compiler-generated
+                            if (mType.IsValueType && mType.ReflectedType != null && string.Equals(mType.ReflectedType.Name, "<PrivateImplementationDetails>", StringComparison.Ordinal))
+                                continue;
+
+                            // Skip if outer type is hidden
+                            if (mType.DeclaringType != null && IsHideAttributes(mType.DeclaringType.GetCustomAttributes(true)))
+                                continue;
+
+                            // Blacklist some types
+                            if (typeof(TypeConverter).IsAssignableFrom(mType) ||
+                                typeof(IHistoryAction).IsAssignableFrom(mType) ||
+                                (mType.Namespace != null && mType.Namespace.StartsWith("Newtonsoft.Json")))
+                                continue;
+                        }
+
                         AddItem(new TypeItemView(type, attributes));
                     }
                 }
@@ -113,6 +131,17 @@ namespace FlaxEditor.GUI
             SortItems();
         }
 
+        private bool IsHideAttributes(object[] attributes)
+        {
+            return attributes.FirstOrDefault(IsHideAttribute) == null;
+        }
+
+        private bool IsHideAttribute(object attr)
+        {
+            return attr is HideInEditorAttribute || 
+                   attr is System.Runtime.CompilerServices.CompilerGeneratedAttribute;
+        }
+
         private void OnItemClicked(Item item)
         {
             _selected(((TypeItemView)item).Type);
diff --git a/Source/Editor/GUI/Timeline/GUI/KeyframesEditor.cs b/Source/Editor/GUI/Timeline/GUI/KeyframesEditor.cs
index 797a0a044..7ee6cb19d 100644
--- a/Source/Editor/GUI/Timeline/GUI/KeyframesEditor.cs
+++ b/Source/Editor/GUI/Timeline/GUI/KeyframesEditor.cs
@@ -8,7 +8,6 @@ using System.Text;
 using FlaxEditor.CustomEditors;
 using FlaxEditor.GUI.ContextMenu;
 using FlaxEditor.Options;
-using FlaxEditor.Scripting;
 using FlaxEngine;
 using FlaxEngine.GUI;
 using FlaxEngine.Json;
diff --git a/Source/Editor/Undo/UndoActionBase.cs b/Source/Editor/Undo/UndoActionBase.cs
index e3fefb355..957eee82b 100644
--- a/Source/Editor/Undo/UndoActionBase.cs
+++ b/Source/Editor/Undo/UndoActionBase.cs
@@ -42,7 +42,7 @@ namespace FlaxEditor
     /// </summary>
     /// <typeparam name="TData">The type of the data. Must have <see cref="SerializableAttribute"/>.</typeparam>
     /// <seealso cref="FlaxEditor.IUndoAction" />
-    [Serializable]
+    [Serializable, HideInEditor]
     public abstract class UndoActionBase<TData> : IUndoAction where TData : struct
     {
         /// <summary>
diff --git a/Source/Editor/Utilities/Units.cs b/Source/Editor/Utilities/Units.cs
index 64977c18b..4c0b5b2ba 100644
--- a/Source/Editor/Utilities/Units.cs
+++ b/Source/Editor/Utilities/Units.cs
@@ -5,7 +5,7 @@ namespace FlaxEditor.Utilities;
 /// <summary>
 /// Units display utilities for Editor.
 /// </summary>
-public class Units
+public static class Units
 {
     /// <summary>
     /// Factor of units per meter.