public static class SitecoreHelper
{
    public static HtmlString DynamicPlaceholder(this Sitecore.Mvc.Helpers.SitecoreHelper helper, string dynamicKey)
    {
        var currentRenderingId = RenderingContext.Current.Rendering.UniqueId;
        return helper.Placeholder(string.Format("{0}_{1}", dynamicKey, currentRenderingId));
    }
}

/// <summary>
/// Handles changing context to the references dynamic "master" renderings settings for inserting the allowed controls for the placeholder and making it editable
/// </summary>
public class GetDynamicKeyAllowedRenderings : GetAllowedRenderings
{
    //text that ends in a GUID
    private const string DYNAMIC_KEY_REGEX = @"(.+)_[dw]{8}-([dw]{4}-){3}[dw]{12}";

    public new void Process(GetPlaceholderRenderingsArgs args)
    {
        Assert.IsNotNull(args, "args");

        string placeholderKey = args.PlaceholderKey;
        Regex regex = new Regex(DYNAMIC_KEY_REGEX);
        Match match = regex.Match(placeholderKey);
        if (match.Success && match.Groups.Count > 0)
        {
            placeholderKey = match.Groups[1].Value;
        }
        else
        {
            return;
        }
        // Same as Sitecore.Pipelines.GetPlaceholderRenderings.GetAllowedRenderings but with fake placeholderKey
        Item placeholderItem = null;
        if (ID.IsNullOrEmpty(args.DeviceId))
        {
            placeholderItem = Client.Page.GetPlaceholderItem(placeholderKey, args.ContentDatabase,
                                                             args.LayoutDefinition);
        }
        else
        {
            using (new DeviceSwitcher(args.DeviceId, args.ContentDatabase))
            {
                placeholderItem = Client.Page.GetPlaceholderItem(placeholderKey, args.ContentDatabase,
                                                                 args.LayoutDefinition);
            }
        }
        List<Item> collection = null;
        if (placeholderItem != null)
        {
            bool flag;
            args.HasPlaceholderSettings = true;
            collection = this.GetRenderings(placeholderItem, out flag);
            if (flag)
            {
                args.CustomData["allowedControlsSpecified"] = true;
                args.Options.ShowTree = false;
            }
        }
        if (collection != null)
        {
            if (args.PlaceholderRenderings == null)
            {
                args.PlaceholderRenderings = new List<Item>();
            }
            args.PlaceholderRenderings.AddRange(collection);
        }
    }
}

/// <summary>
/// Replaces the Displayname of the Placeholder rendering with the dynamic "parent"
/// </summary>
public class GetDynamicPlaceholderChromeData : GetChromeDataProcessor
{
    //text that ends in a GUID
    private const string DYNAMIC_KEY_REGEX = @"(.+)_[dw]{8}-([dw]{4}-){3}[dw]{12}";

    public override void Process(GetChromeDataArgs args)
    {
        Assert.ArgumentNotNull(args, "args");
        Assert.IsNotNull(args.ChromeData, "Chrome Data");
        if ("placeholder".Equals(args.ChromeType, StringComparison.OrdinalIgnoreCase))
        {
            string argument = args.CustomData["placeHolderKey"] as string;

            string placeholderKey = argument;
            Regex regex = new Regex(DYNAMIC_KEY_REGEX);
            Match match = regex.Match(placeholderKey);
            if (match.Success && match.Groups.Count > 0)
            {
                // Is a Dynamic Placeholder
                placeholderKey = match.Groups[1].Value;
            }
            else
            {
                return;
            }

            // Handles replacing the displayname of the placeholder area to the master reference
            Item item = null;
            if (args.Item != null)
            {
                string layout = ChromeContext.GetLayout(args.Item);
                item = Sitecore.Client.Page.GetPlaceholderItem(placeholderKey, args.Item.Database, layout);
                if (item != null)
                {
                    args.ChromeData.DisplayName = item.DisplayName;
                }
                if ((item != null) && !string.IsNullOrEmpty(item.Appearance.ShortDescription))
                {
                    args.ChromeData.ExpandedDisplayName = item.Appearance.ShortDescription;
                }
            }
        }
    }
}

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <pipelines>
       <getPlaceholderRenderings>
           <processor type="MyCustomNamespace.Pipelines.GetPlaceholderRenderings.GetDynamicKeyAllowedRenderings,MyCustomNamespace" patch:before="processor[@type='Sitecore.Pipelines.GetPlaceholderRenderings.GetAllowedRenderings,Sitecore.Kernel']"/>
       </getPlaceholderRenderings>
       <getChromeData>
           <processor type="Sitecore.Pipelines.GetChromeData.GetPlaceholderChromeData, Sitecore.Kernel">
              <patch:attribute name="type">MyCustomNamespace.Pipelines.GetPlaceholderRenderings.GetDynamicPlaceholderChromeData,MyCustomNamespace</patch:attribute>
           </processor>
       </getChromeData>
    </pipelines>
  </sitecore>
</configuration>

<getChromeData>
  <processor type="MyCustomNamespace.Pipelines.GetChromeData.GetDynamicPlaceholderChromeData,MyCustomNamespace" patch:after="processor[@type='Sitecore.Pipelines.GetChromeData.GetPlaceholderChromeData, Sitecore.Kernel']"/>
</getChromeData>