Custom Sitecore Tokens and replacement

MasterVariablesReplacer.config

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <settings>
      <setting name="MasterVariablesReplacer">
        <patch:attribute name="value">Sitecore.Sharedsource.Data.MasterVariablesReplacer,Sitecore.Sharedsource</patch:attribute>
      </setting>
    </settings>
  </sitecore>
</configuration>

MasterVariablesReplacer.cs

namespace Sitecore.Sharedsource.Data
{
  using System;
  using System.Collections.Generic;
  
  using SC = Sitecore;
  
  public class MasterVariablesReplacer : SC.Data.MasterVariablesReplacer
  {
    public override string Replace(string text, SC.Data.Items.Item targetItem)
    {
      SC.Diagnostics.Assert.ArgumentNotNull(text, "text");
      SC.Diagnostics.Assert.ArgumentNotNull(targetItem, "targetItem");
      string result = this.ReplaceValues(
        text,
        () => targetItem.Name,
        () => targetItem.ID.ToString(),
        () => SC.Data.Items.ItemUtil.GetParentName(targetItem),
        () => targetItem.ParentID.ToString());
      return result;
    }
  
    private string ReplaceValues(
      string text,
      Func<string> defaultName,
      Func<string> defaultId,
      Func<string> defaultParentName,
      Func<string> defaultParentId)
    {
      if ((text.Length != 0) && (text.IndexOf('$') >= 0))
      {
        SC.Text.ReplacerContext context = this.GetContext();
  
        if (context != null)
        {
          foreach (KeyValuePair<string, string> pair in context.Values)
          {
            text = text.Replace(pair.Key, pair.Value);
          }
        }
  
        text = this.ReplaceWithDefault(text, "$name", defaultName, context);
        text = this.ReplaceWithDefault(text, "$id", defaultId, context);
        text = this.ReplaceWithDefault(text, "$parentid", defaultParentId, context);
        text = this.ReplaceWithDefault(text, "$parentname", defaultParentName, context);
        text = this.ReplaceWithDefault(text, "$date", () => SC.DateUtil.IsoNowDate, context);
        text = this.ReplaceWithDefault(text, "$time", () => SC.DateUtil.IsoNowTime, context);
        text = this.ReplaceWithDefault(text, "$now", () => SC.DateUtil.IsoNow, context);
        text = this.ReplaceWithDefault(text, "$user", () => SC.Context.User.LocalName, context);
      }
  
      return text;
    }
  
    private string ReplaceWithDefault(
      string text, 
      string variable, 
      Func<string> defaultValue, 
      SC.Text.ReplacerContext context)
    {
      if ((context != null) && context.Values.ContainsKey(variable))
      {
        return text;
      }
  
      if (text.IndexOf(variable, StringComparison.InvariantCulture) < 0)
      {
        return text;
      }
  
      return text.Replace(variable, defaultValue());
    }
  }
}

Adding Custom Value Token in Sitecore CMS
https://community.sitecore.net/technical_blogs/b/sitecorejohn_blog/posts/add-custom-standard-values-tokens-in-the-sitecore-asp-net-cms