1. Create on HCP server file C:\Program Files (x86)\Atomia\HostingControlPanel\bin\Transformation Files\Atomia.Web.Plugin.Databases.dll.PhpMyAdmin.config

<?xml version="1.0" encoding="utf-8"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <appConfig xmlns="Atomia.Web.Base.Configs">
	<pluginSettingsList>
      <pluginSettingsPlugin pluginName="Databases" xdt:Locator="Match(pluginName)">
		<pluginSetting name="MysqlPHPMyAdminAddress" value="http://phpmyadmin.yourdomain.com" xdt:Transform="SetAttributes(value)" xdt:Locator="Match(name)" />
      </pluginSettingsPlugin>
    </pluginSettingsList>
  </appConfig>
</configuration>

2. Run C:\Program Files (x86)\Atomia\HostingControlPanel\Recreate config files

3. Optional, setup phpmyadmin.yourdomain.com for https access with your *.yourdomain.com certificate.  Also, in transformation file above change value to "https://phpmyadmin.yourdomain.com"