ExampleClass.cs

using System.Linq;
using UnityEditor;
using UnityEngine;

public static class ExampleClass
{
    private static readonly Color mDisabledColor = new Color( 1, 1, 1, 0.5f );

    private const int WIDTH     = 16;
    private const int HEIGHT    = 16;

    [InitializeOnLoadMethod]
    private static void Example()
    {
        EditorApplication.hierarchyWindowItemOnGUI += OnGUI;
    }
    
    private static void OnGUI( int instanceID, Rect selectionRect )
    {
        var go = EditorUtility.InstanceIDToObject( instanceID ) as GameObject;

        if ( go == null )
        {
            return;
        }
        
        var pos     = selectionRect;
        pos.x       = pos.xMax - WIDTH;
        pos.width   = WIDTH;
        pos.height  = HEIGHT;

        var components = go
            .GetComponents<Component>()
            .Where( c => c != null )
            .Where( c => !( c is Transform ) )
            .Reverse();

        var current = Event.current;

        foreach ( var c in components )
        {
            Texture image = AssetPreview.GetMiniThumbnail( c );

            if ( image == null && c is MonoBehaviour )
            {
                var ms      = MonoScript.FromMonoBehaviour( c as MonoBehaviour );
                var path    = AssetDatabase.GetAssetPath( ms );
                image       = AssetDatabase.GetCachedIcon( path );
            }

            if ( image == null )
            {
                continue;
            }
            
            if ( current.type == EventType.MouseDown && 
                 pos.Contains( current.mousePosition ) )
            {
                c.SetEnable( !c.IsEnabled() );
            }
            
            var color = GUI.color;
            GUI.color = c.IsEnabled() ? Color.white : mDisabledColor;
            GUI.DrawTexture( pos, image, ScaleMode.ScaleToFit );
            GUI.color = color;
            pos.x -= pos.width;
        }
    }

    public static bool IsEnabled( this Component self )
    {
        if ( self == null )
        {
            return true;
        }

        var type        = self.GetType();
        var property    = type.GetProperty( "enabled", typeof( bool ) );
        
        if ( property == null )
        {
            return true;
        }

        return ( bool )property.GetValue( self, null );
    }

    public static void SetEnable( this Component self, bool isEnabled )
    {
        if ( self == null )
        {
            return;
        }

        var type        = self.GetType();
        var property    = type.GetProperty( "enabled", typeof( bool ) );
        
        if ( property == null )
        {
            return;
        }

        property.SetValue( self, isEnabled, null );
    }
}