Extending SQL Server Object Explorer Context Menus

This should hopefully be a quick one. I've been trying to add a custom tool to the Sql Server object explorer in VS2015, using the SSDT 2016 CTP. I'd like to add it at the database node level like this:



However, I can't find the appropriate parent to which I can add my custom command. I've tried using 

<Parent guid="guid_SE_MenuGroup" id="IDM_SE_TOOLBAR_SERVEREXPLORER"/>

as recommended here: https://social.msdn.microsoft.com/Forums/vstudio/en-US/9c4fcf25-6937-464f-ba89-ab61e2a86c99/add-a-new-button-to-the-server-explorer-toolbar?forum=vsx#ebc1b3a8-9311-48b8-8b81-f7418ec33def

but to this  point, no joy.

Can anyone please guide me in the correct direction on this?

Andrew Raymond Sr. Software Engineer, Mitchell 1 MCAD .NET